Programa HiWish

HiWish es un programa creado por la NASA para que cualquier persona pueda sugerir un lugar para fotografiar con la cámara HiRISE del Mars Reconnaissance Orbiter . ^{[1] [2] [3]} Comenzó en enero de 2010. En los primeros meses del programa, 3000 personas se inscribieron para utilizar HiRISE. ^{[4] [5]} Las primeras imágenes se publicaron en abril de 2010. ^[6] El público hizo más de 12 000 sugerencias; se hicieron sugerencias de objetivos en cada uno de los 30 cuadrángulos de Marte. Las imágenes seleccionadas publicadas se utilizaron para tres charlas en la 16.ª Convención Anual de la Sociedad Internacional de Marte. A continuación se muestran algunas de las más de 4224 imágenes que se han publicado desde el programa HiWish hasta marzo de 2016. ^[7]

Algunos paisajes parecen glaciares que salen de los valles de las montañas de la Tierra. Otros tienen un aspecto ahuecado, como un glaciar después de que casi todo el hielo haya desaparecido. Lo que queda son las morrenas, la suciedad y los escombros que arrastra el glaciar. El centro está ahuecado porque el hielo ha desaparecido casi por completo. ^[8] Estos supuestos glaciares alpinos se han denominado formas similares a glaciares (GLF) o flujos similares a glaciares (GLF). ^[9] Las formas similares a glaciares son un término posterior y tal vez más preciso porque no podemos estar seguros de que la estructura se esté moviendo en ese momento. ^[10]

Glaciar marciano desplazándose por un valle, visto por HiRISE en el marco del programa HiWish

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  Posible glaciar que desciende por un valle y se extiende sobre una llanura. El rectángulo muestra una porción que se amplía en la siguiente imagen.
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  Ampliación de la zona del rectángulo de la imagen anterior. Esta zona se denominaría morrena en un glaciar alpino de la Tierra.
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  Huecos bien desarrollados de relleno de cráter concéntrico, como se ve mediante HiRISE en el marco del programa HiWish
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  Glaciar en el fondo de un cráter, tal como lo ve HiRISE en el marco del programa HiWish. Las grietas del glaciar pueden ser hendiduras. También hay un sistema de cárcavas en la pared del cráter.
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  Glaciar saliendo del valle, como se ve con HiRISE en el programa HiWish. La ubicación es el borde del cráter Moreux . La ubicación es el cuadrángulo del lago Ismenius .

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  Vista amplia de flujos en forma de lengua, como los ve HiRISE bajo el programa HiWish
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  Vista cercana de flujos con forma de lengua, como los ve HiRISE bajo el programa HiWish

Las grietas radiales y concéntricas que se ven aquí son comunes cuando las fuerzas penetran una capa frágil, como una roca arrojada a través de una ventana de vidrio. Estas fracturas en particular probablemente fueron creadas por algo que emergió desde debajo de la frágil superficie marciana. El hielo puede haberse acumulado debajo de la superficie en forma de lente, lo que produjo estos montículos agrietados. El hielo, al ser menos denso que la roca, empujó hacia arriba en la superficie y generó estos patrones similares a una telaraña. Un proceso similar crea montículos de tamaño similar en la tundra ártica de la Tierra. Estas características se denominan "pingos", una palabra inuit. ^[11] Los pingos contendrían hielo de agua pura; por lo tanto, podrían ser fuentes de agua para los futuros colonos de Marte. Muchas características que se parecen a los pingos de la Tierra se encuentran en Utopia Planitia (~35-50° N; ~80-115° E). ^​​[12]

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  Posibles pingos con escala, como los que ve HiRISE en el programa HiWish
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  Vista cercana de un posible pingo con escala, como lo ve HiRISE bajo el programa HiWish

Hay muchas pruebas de que en Marte el agua fluía por los valles fluviales. Las imágenes tomadas desde la órbita muestran valles sinuosos, valles ramificados e incluso meandros con lagos en forma de meandro . ^[13] Algunos de ellos son visibles en las imágenes que aparecen a continuación.

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  Canal en el suelo del cráter Newton, visto por HiRISE en el marco del programa HiWish
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  Canal ramificado, como lo ve HiRISE bajo el programa HiWish
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  Canal, tal como lo ve HiRISE en el programa HiWish
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  Canal ramificado, como lo ve HiRISE bajo el programa HiWish
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  Lago Oxbow , visto por HiRISE en el marco del programa HiWish
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  Los valles vistos por HiRISE en el marco del programa HiWish
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  Canal en Arabia, visto por HiRISE en el programa HiWish
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  Sistema de canales que atraviesa parte de un cráter, tal como lo ve HiRISE en el marco del programa HiWish
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  Canales, tal como los ve HiRISE en el programa HiWish. El arroyo parece haber erosionado una colina.
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  Canal que muestra un antiguo meandro y un atajo, tal como lo ve HiRISE en el programa HiWish. La ubicación es el cuadrángulo de Memnonia .
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  Canal en el fondo del valle, visto por HiRISE en el marco del programa HiWish. La ubicación es el cuadrángulo de Eridania .
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  Vista cercana del canal en el cuadrángulo del lago Ismenius , como lo ve HiRISE bajo el programa HiWish
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  Canal con valle colgante en el cuadrángulo del lago Ismenius, visto por HiRISE en el marco del programa HiWish
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  Valles colgantes en Aram Chaos , vistos por HiRISE en el marco del programa HiWish
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  Vista amplia de los canales en el cuadrángulo del lago Ismenius, tal como los ve HiRISE con el programa HiWish

Las formas aerodinámicas representan más evidencia de que en el pasado hubo agua fluyendo en Marte. El agua moldeó las características y las convirtió en formas aerodinámicas.

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  Función optimizada, como se ve en HiRISE bajo el programa HiWish. La ubicación es el cuadrángulo de Memnonia .
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  Canal, tal como lo ve HiRISE con el programa HiWish. Las formas aerodinámicas se indican con flechas. La ubicación es el cuadrángulo de Faetón .

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  Vista amplia de formas aerodinámicas en el cuadrángulo de Amenthes , como se ve con HiRISE bajo el programa HiWish
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  Vista en primer plano de formas aerodinámicas, como las observa HiRISE con el programa HiWish. La flecha indica la dirección del agua que fluía en el pasado.
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  Vista cercana de formas aerodinámicas, como las ve HiRISE bajo el programa HiWish
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  Vista cercana de formas aerodinámicas, como las ve HiRISE bajo el programa HiWish
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  Vista cercana de formas aerodinámicas, como las ve HiRISE bajo el programa HiWish
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  Vista cercana de la forma aerodinámica, como la ve HiRISE bajo el programa HiWish
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  Formas estilizadas, como las que se ven en HiRISE con el programa HiWish. La ubicación es el cuadrángulo Elysium .

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  Imágenes de HiRISE que muestran el descubrimiento de un nuevo cráter con el programa HiWish
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  Nuevo cráter, tal como lo vio HiRISE en el marco del programa HiWish. El nuevo cráter indicado con la flecha blanca tiene unos 10 metros de diámetro y probablemente se creó por la colisión con un objeto del tamaño de una sandía grande. Este cráter no apareció en imágenes anteriores de la misma región.

Muchos lugares de Marte tienen dunas de arena . Las dunas están cubiertas por una escarcha estacional de dióxido de carbono que se forma a principios de otoño y permanece hasta finales de primavera. Muchas dunas marcianas se parecen mucho a las dunas terrestres, pero las imágenes adquiridas por el Experimento Científico de Imágenes de Alta Resolución en el Mars Reconnaissance Orbiter han demostrado que las dunas marcianas en la región del polo norte están sujetas a modificaciones a través del flujo de granos desencadenado por la sublimación estacional de CO ₂ , un proceso que no se observa en la Tierra. Muchas dunas son negras porque se derivan de la roca volcánica oscura basalto. Los mares de arena extraterrestres como los que se encuentran en Marte se conocen como "undae", del latín que significa olas.

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  Dunas en dos cráteres, vistas por HiRISE bajo el programa HiWish
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  Dunas entre cráteres, como las observa HiRISE en el programa HiWish. Algunas de ellas son barjanes.
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  Dunas en el fondo de un cráter, como las observa HiRISE con el programa HiWish. La mayoría son barjanes. El recuadro muestra la ubicación de la siguiente imagen. La ubicación es el cuadrángulo de Eridania .
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  Dunas en el fondo de un cráter, como las ve HiRISE con el programa HiWish. La mayoría son barjanes. Nota: esta es una ampliación del centro de la imagen anterior.
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  Dunas, vistas por HiRISE en el marco del programa HiWish. La ubicación es el cuadrángulo de Eridania .
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  Descongelación de dunas y hielo en canales de polígonos, como se ve con HiRISE en el marco del programa HiWish
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  Vista en color de dunas y hielo descongelados en canales de polígonos, como se ve con HiRISE bajo el programa HiWish
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  Superficie descongelada, como la ve HiRISE con el programa HiWish. La escarcha está desapareciendo en parches de una duna. Los límites de los canales alrededor de las formas poligonales aún contienen escarcha; por eso son blancos. Nota: el lado norte (lado cerca de la parte superior) no se ha descongelado porque el sol está entrando desde el otro lado.
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  Vista panorámica de las dunas del cráter Moreux , tal como las vio HiRISE en el marco del programa HiWish
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  Dunas en el cuadrilátero de Mare Tyrrhenum , vistas por HiRISE bajo el programa HiWish
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  Vista cercana de las dunas en el cuadrángulo de Mare Tyrrhenum , como las vio HiRISE en el marco del programa HiWish
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  Vista en color de cerca de las dunas del cuadrángulo Mare Tyrrhenum , tal como las ve HiRISE con el programa HiWish. Se ven ondulaciones en la superficie de las dunas.
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  Vista cercana y en color de las dunas de arena en forma de domo, como las ve HiRISE en el marco del programa HiWish

Algunos de los objetivos sugeridos se convirtieron en posibles sitios para una misión Rover en 2020. Los objetivos estaban en Firsoff (cráter) y Holden . Estas ubicaciones fueron elegidas como dos de las 26 ubicaciones consideradas para una misión que buscará señales de vida y recolectará muestras para un posterior regreso a la Tierra. ^{[14] [15] [16]}

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  Capas del cráter Firsoff, vistas por HiRISE con el programa HiWish. Nota: este campo de imagen se puede encontrar en la imagen anterior de las capas del cráter Firsoff, vistas por la cámara CTX (a bordo del Mars Reconnaissance Orbiter).
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  Primer plano de las capas del cráter Firsoff, tal como las ve HiRISE. Nota: esta es una ampliación de la imagen anterior del cráter Firsoff.
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  Capas en el cráter Firsoff con un recuadro que muestra el tamaño de un campo de fútbol. Fotografía tomada por HiRISE bajo el programa HiWish.
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  Capas y fallas del cráter Firsoff, tal como las ve HiRISE con el programa HiWish. Las flechas indican una falla grande, pero hay otras más pequeñas en la imagen.
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  Parte del delta del cráter Holden , visto por HiRISE en el marco del programa HiWish. El cráter Holden es un posible lugar de aterrizaje para un vehículo explorador de Marte programado para 2020. ^[17]
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  Vista cercana de la imagen anterior que muestra las capas, como se ve con HiRISE bajo el programa HiWish y ampliada con HiView

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  Depresiones al este de Albor Tholus, observadas por HiRISE en el marco del programa HiWish
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  Parte de una fosa en Elysium Planitia , tal como se ve en HiRISE con el programa HiWish. El color azul indica posibles heladas estacionales.
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  Deslizamiento de tierra en un cráter, visto por HiRISE en el marco del programa HiWish. Imagen del cuadrángulo de Iapygia .
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  Vista panorámica de Buttes y Mesas, como las vio HiRISE en el marco del programa HiWish. La ubicación es el cuadrángulo Elysium .
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  Buttes y mesetas, como se ven en HiRISE con el programa HiWish. Nota: esta es una ampliación de la imagen anterior.
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  Mesas, vistas por HiRISE con el programa HiWish. Nota: esta es una ampliación de una imagen anterior.

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  Capas y rayas oscuras en pendientes, como las observa HiRISE con el programa HiWish
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  Rayas oscuras en la ladera de la meseta, como se observan con HiRISE en el programa HiWish. La ubicación es el cuadrángulo Amazonis .
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  Primer plano de algunas capas bajo la roca de la cubierta de un cráter de pedestal y una franja oscura en la pendiente, como se ve con HiRISE en el programa HiWish
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  Rayas y capas oscuras en la pendiente cerca de un cráter de pedestal, como las observa HiRISE con el programa HiWish. Las flechas muestran los pequeños puntos de inicio de las rayas.
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  Rayas oscuras en la pendiente del montículo en Lycus Sulci en el cuadrángulo de Diacria , como se ve con HiRISE en el programa HiWish
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  Capas en valles y vetas oscuras de laderas, como se observan con HiRISE en el programa HiWish. La ubicación es el cuadrángulo Amazonis .

Las líneas de pendiente recurrentes son pequeñas rayas oscuras en las laderas que se alargan en las estaciones cálidas. Pueden ser evidencia de agua líquida. ^{[18] [19] [20]} Sin embargo, sigue habiendo debate sobre si se necesita agua o mucha agua. ^{[21] [22] [23] [24]}

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  Vista amplia de parte de Valles Marineris, tal como la vio HiRISE con el programa HiWish. El recuadro muestra la ubicación de las líneas de pendiente recurrentes que se amplían en la siguiente imagen.
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  Vista en color de las líneas de pendiente recurrentes, como las ve HiRISE con el programa HiWish. Las flechas señalan algunas de las líneas de pendiente recurrentes ^[25]

En muchos lugares de Marte se observan rocas dispuestas en capas. Las rocas pueden formar capas de diversas maneras. Los volcanes, el viento o el agua pueden producir capas. ^[26] Las capas pueden endurecerse por la acción del agua subterránea.

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  Capas expuestas en la base de un grupo de colinas en Mangala Valles en el cuadrángulo de Memnonia , como se ve en HiRISE bajo el programa HiWish. Las flechas señalan rocas que se encuentran en fosas. Las fosas pueden haberse formado por los vientos, el calor de las rocas al derretir el hielo del suelo o algún otro proceso.
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  Buttes, vistos por HiRISE en el marco del programa HiWish. Los buttes tienen rocas estratificadas con una roca resistente y dura en la parte superior que protege las rocas subyacentes de la erosión.
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  Butte en el cráter Crommelin, visto por HiRISE en el marco del programa HiWish. La ubicación es el cuadrángulo Oxia Palus .
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  Capas del cráter Crommelin, vistas por HiRISE en el marco del programa HiWish. La ubicación es el cuadrángulo Oxia Palus .

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  Montículo estratificado en el suelo del cráter Danielson, visto por HiRISE en el marco del programa HiWish
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  Vista cercana y en color de las capas y el polvo oscuro en el suelo del cráter Danielson, como lo ve HiRISE bajo el programa HiWish
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  Vista en color de cerca de las capas y el polvo oscuro en el suelo del cráter Danielson, como se ve con HiRISE en el programa HiWish. Se ven rocas en la imagen.
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  Vista en color de cerca de las capas y el polvo oscuro del suelo del cráter Danielson, tal como se observa con HiRISE en el programa HiWish. Las fallas se indican con flechas.
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  Vista de cerca de las capas del suelo del cráter Danielson, como las ve HiRISE con el programa HiWish. Algunas fallas son visibles en la imagen.

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  Colina de color claro en el fondo del cráter, como se ve con HiRISE en el programa HiWish. Las flechas muestran afloramientos de material de color claro. El material de color claro es probablemente rico en sulfatos y similar al material examinado por Spirit Rover, y es probable que alguna vez cubriera todo el fondo. Otras imágenes a continuación muestran ampliaciones de la colina. La ubicación es el cuadrángulo del seno Margaritifer .
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  Ampliación de la meseta blanca, tal como la ve HiRISE en el programa HiWish. El recuadro muestra el tamaño de un campo de fútbol.
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  Vista más cercana hacia la cima de la colina blanca, como la ve HiRISE en el programa HiWish. El recuadro muestra el tamaño de un campo de fútbol.
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  Parte superior de una colina blanca, como se ve en HiRISE con el programa HiWish. El recuadro muestra el tamaño de un campo de fútbol.

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  Terreno en capas en el cuadrángulo Aeolis , como lo ve HiRISE bajo el programa HiWish.
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  Vista amplia del terreno estratificado, como lo vio HiRISE en el programa HiWish. La ubicación está al noreste del cráter Gale en el cuadrángulo Aeolis .
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  Vista cercana del montículo con capas, como se ve con HiRISE en el programa HiWish. Nota: esta es una ampliación de la imagen anterior.
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  Vista cercana del montículo con capas, como se ve con HiRISE en el programa HiWish. Nota: esta es una ampliación de una imagen anterior.
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  Capas en Arabia, como las ve HiRISE bajo el programa HiWish.
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  Vista amplia de una parte del cráter Danielson, vista por HiRISE en el marco del programa HiWish
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  Ampliación de la imagen anterior del cráter Danielson, tal como la vio HiRISE con el programa HiWish. El recuadro representa el tamaño de un campo de fútbol.
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  Primer plano de las capas del cráter Danielson, como las vio HiRISE en el marco del programa HiWish: se ven rocas y arena oscura
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  Primer plano de las capas en la vaguada al sur de Ius Chasma, como se ve con HiRISE en el marco del programa HiWish
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  Primer plano de las capas del cráter Lotto, tal como las vio HiRISE en el marco del programa HiWish
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  Capas, como las ve HiRISE con el programa HiWish. La ubicación es Tempe Terra .
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  Capas, como las ve HiRISE con el programa HiWish. La ubicación es Tempe Terra. Nota: esta es una ampliación de la imagen anterior.

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  Vista de cerca de las capas, como las ve HiRISE con el programa HiWish. Al menos una capa tiene un tono claro, lo que puede indicar minerales hidratados.
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  Vista cercana de las capas, como las ve HiRISE con el programa HiWish

Este grupo de capas que se encuentran en un cráter provienen todas del cuadrángulo Arabia .

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  Vista amplia de las capas del cráter, tal como las vio HiRISE con el programa HiWish. Partes de esta imagen se amplían en otras imágenes que aparecen a continuación.
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  Vista detallada de las capas, como las ve HiRISE con el programa HiWish. El recuadro muestra el tamaño de un campo de fútbol.
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  Vista detallada de las capas, como las ve HiRISE con el programa HiWish. El recuadro muestra el tamaño de un campo de fútbol.
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  Vista detallada de las capas, como las ve HiRISE con el programa HiWish. El recuadro muestra el tamaño de un campo de fútbol.
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  Vista cercana de las capas, como las ve HiRISE con el programa HiWish
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  Vista cercana de las capas, como las ve HiRISE con el programa HiWish
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  Vista cercana de las capas, como las ve HiRISE con el programa HiWish
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  Vista cercana de las capas, como las ve HiRISE con el programa HiWish
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  Vista cercana de las capas, como las ve HiRISE con el programa HiWish

El siguiente grupo de terreno estratificado proviene de los Valles de Louros en el cuadrángulo de Coprates .

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  Vista panorámica de las capas de Louros Valles , tal y como las ve HiRISE en el marco del programa HiWish
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  Vista detallada de las capas de Louros Valles, tal como las ve HiRISE con el programa HiWish. Nótese que se trata de una ampliación de una imagen anterior.
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  Vista detallada de las capas de Louros Valles, tal como las ve HiRISE con el programa HiWish. Nótese que se trata de una ampliación de una imagen anterior.
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  Vista detallada de las capas de Louros Valles, tal como las ve HiRISE con el programa HiWish. Nótese que se trata de una ampliación de una imagen anterior.
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  Vista detallada de las capas de Louros Valles, tal como las ve HiRISE con el programa HiWish. Nótese que se trata de una ampliación de una imagen anterior.

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  Capas en la capa de hielo del norte con una discordancia angular, como se ve con HiRISE en el marco del programa HiWish
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  Vista detallada de las capas de la capa de hielo del norte, tal como las observa HiRISE en el marco del programa HiWish. Las flechas señalan una discordancia angular.
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  Vista en color de cerca de las capas de la capa de hielo del norte, como las ve HiRISE en el marco del programa HiWish
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  Capas expuestas en la capa de hielo del norte, vistas por HiRISE en el marco del programa HiWish
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  Close view of layers exposed in northern ice cap, as seen by HiRISE under HiWish program

Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a dendritic alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape.^[27] They are believed to be relatively young because they have few, if any craters. On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research.

Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program. Location is Phaethontis quadrangle.

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  Close-up of gully aprons showing they are free of craters; hence very young. Location is Phaethontis quadrangle. Picture was taken by HiRISE under HiWish program.
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  Gullies on wall of crater, as seen by HiRISE under HiWish program. Location is the Mare Acidalium quadrangle.
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  Close-up of gully channels, as seen by HiRISE under HiWish program. This image shows many streamlined forms and some benches along a channel. These features suggest formation by running water. Benches are usually formed when the water level goes down a bit and stays at that level for a time. Picture was taken with HiRISE under HiWish program. Location is the Mare Acidalium quadrangle. Note this is an enlargement of a previous image.
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  Gullies in crater in Phaethontis quadrangle, as seen by HiRISE under HiWish program
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  Gullies along mesa wall in North Tempe Terra, as seen by HiRISE under HiWish program
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  Close view of gully apron, as seen by HiRISE under HiWish program. Note this is an enlargement of the previous image.
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  Close view of gully alcove, as seen by HiRISE under HiWish program. Note this is an enlargement of a previous image.

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  Gullies in crater, as seen by HiRISE under HiWish program
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  Close view of gullies from previous image The channels are quite curved. Because channels of gullies often form curves, it was thought that they were made by flowing water. Today, it is thought that they could be produced with chunks of dry ice. The image is from HiRISE under HiWish program.
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  Gullies, as seen by HiRISE. The gullies range from very samll to large, as such they may represent different stages in the formation of gullies. The colored strip is about 1 km wide.
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  Small gully This gully may be in its initial state of formation.
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  Gully, as seen by HiRISE
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  Wide view of gullies
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  Close view of gully alcoves Picture is about 1 km across.
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  Close view of gully alcoves Picture is about 1 km across.
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  Close view of gully channels Picture is about 1 km across.

Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past.^[28][29][30] In some places a number of layers are visible in the mantle.^[31]

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  Surface showing appearance with and without mantle covering, as seen by HiRISE, under the HiWish program. Location is Terra Sirenum in Phaethontis quadrangle.
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  Mantle layers, as seen by HiRISE under HiWish program. Location is Eridania quadrangle
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  Close up view of mantle, as seen by HiRISE under the HiWish program. Mantle may be composed of ice and dust that fell from the sky during past climatic conditions. Location is Cebrenia quadrangle.
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  Close view of mantle, as seen by HiRISE under HiWish program. Arrows show craters along edge which highlight the thickness of mantle. Location is Ismenius Lacus quadrangle.
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  Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.

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  Wide view of surface with spots displaying mantle, as seen by HiRISE under HiWish program. Location is the Arcadia quadrangle.
• 
  Close view of mantle, as seen by HiRISE under HiWish program
• 
  Close view of mantle, as seen by HiRISE under HiWish program

It fell as snow and ice-coated dust. There is good evidence that this mantle is ice-rich. The shapes of the polygons common on many surfaces suggest ice-rich soil. High levels of hydrogen (probably from water) have been found with Mars Odyssey.^{[32][33][34][35][36]} Thermal measurements from orbit suggest ice.^[37][38] The Phoenix (spacecraft) discovered water ice with made direct observations since it landed in a field of polygons.^[39][40] In fact, its landing rockets exposed pure ice. Theory had predicted that ice would be found under a few cm of soil. This mantle layer is called "latitude dependent mantle" because its occurrence is related to the latitude. It is this mantle that cracks and then forms polygonal ground. This cracking of ice-rich ground is predicted based on physical processes.^{[41][42][43][44][45][46][47]}

Polygonal, patterned ground is quite common in some regions of Mars.^{[48][49][50][51][46][52][53]} It is commonly believed to be caused by the sublimation of ice from the ground. Sublimation is the direct change of solid ice to a gas. This is similar to what happens to dry ice on the Earth. Places on Mars that display polygonal ground may indicate where future colonists can find water ice. Patterned ground forms in a mantle layer, called latitude dependent mantle, that fell from the sky when the climate was different.^{[28][29][54][55]}

• 
  Wide view of crater containing polygons with frost in the low parts, as seen by HiRISE under the HiWish program
• 
  Closer view of polygons with frost in the low parts, as seen by HiRISE under the HiWish program
• 
  Still closer view of polygons, as seen by HiRISE under the HiWish program
• 
  Close view of polygons with frost in the low parts, as seen by HiRISE under the HiWish program. Circular shapes are also visible.

• 
  High center polygons, shown with arrows, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView.
• 
  Scalloped terrain labeled with both low center polygons and high center polygons, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView.
• 
  High and low center polygons, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView.
• 
  Close-up of high center polygons seen by HiRISE under HiWish program. Troughs between polygons are easily visible in this view. Location is Ismenius Lacus quadrangle.
• 
  Low center polygons, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView. Location is Casius quadrangle.
• 
  Close view of snout of glacier, as seen by HiRISE under the HiWish program. High center polygons are visible. Box shows size of football field.
• 
  Close view of high center polygons near glacier, as seen by HiRISE under the HiWish program. Box shows size of football field.
• 
  Close view of high center polygons near glacier, as seen by HiRISE under the HiWish program

• 
  Wide view of a group of channels, as seen by HiRISE under HiWish project Some parts of the surface show patterned ground when enlarged.
• 
  Patterned ground, as seen by HiRISE under HiWish program. This is a close up from previous image.
• 
  Ridges, as seen by HiRISE under HiWish program. This is a close up from a previous image.
• 
  Color view of surface in a previous image, as seen by HiRISE under HiWish program
• 
  Color image of patterned ground, enlarged from a previous image, as seen by HiRISE under HiWish program

• 
  Wide view of polygons, as seen by HiRISE under HiWish program. Parts of this image are enlarged in following images. The location is the Noachis quadrangle.
• 
  Polygons, as seen by HiRISE under HiWish program
• 
  Close view of polygons, as seen by HiRISE under HiWish program. Arrow point to boulders that sit inside of small craters.
• 
  Close view of polygons, as seen by HiRISE under HiWish program
• 
  Close view of polygons, as seen by HiRISE under HiWish program

HiRISE images taken under the HiWish program found triangular shaped depressions in Milankovic Crater that researchers found contain vast amounts of ice that are found under only 1–2 meters of soil. These depressions contain water ice in the straight wall that faces the pole, according to the study published in the journal Science. Eight sites were found with Milankovic Crater being the only one in the northern hemisphere. Research was conducted with instruments on board the Mars Reconnaissance Orbiter (MRO).^{[56][57][58][59][60]}

The following images are ones referred to in this study of subsurface ice sheets.^[61]

• 
  Wide view of part of Milankovic Crater, as seen by HiRISE under HiWish program. Many depressions here contain ice in their walls.
• 
  Close view from a previous image, as seen by HiRISE under HiWish program. The triangular shape of some depressions are noted. The area in the box is enlarged in following images.
• 
  Close view of depression, as seen by HiRISE under HiWish program. Arrows indicate where there is a very thin, 1–2 meter covering on what is believed to be ice.

These triangular depressions are similar to those in scalloped terrain. However scalloped terrain, displays a gentle equator-facing slope and is rounded. Scarps discussed here have a steep pole-facing side and have been found between 55 and 59 degrees north and south latitude^[61] Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south.

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is particularly prominent in the region of Utopia Planitia^[62][63] in the northern hemisphere and in the region of Peneus and Amphitrites Patera^[64][65] in the southern hemisphere. Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. A typical scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp. This topographic asymmetry is probably due to differences in insolation. Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation. This process may still be happening at present.^[66]

On November 22, 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars.^[67] The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.^[68][69]The volume of water ice in the region were based on measurements from the ground-penetrating radar instrument on Mars Reconnaissance Orbiter, called SHARAD. From the data obtained from SHARAD, "dielectric permittivity", or the dielectric constant was determined. The dielectric constant value was consistent with a large concentration of water ice.^[70][71][72]

• 
  Scalloped ground, as seen by HiRISE under HiWish program
• 
  Close-up of scalloped ground, as seen by HiRISE under HiWish program. Surface is divided into polygons; these forms are common where ground freezes and thaws. Note: this is an enlargement of a previous image.
• 
  Scalloped ground, as seen by HiRISE under HiWish program
• 
  Close-up of scalloped ground, as seen by HiRISE under HiWish program. Surface is divided into polygons; these forms are common where ground freezes and thaws. Note: this is an enlargement of a previous image.
• 
  Low center polygons, shown with arrows, as seen by HiRISE under HiWish program. Image was enlarged with HiView.
• 
  Scalloped terrain, as seen by HiRISE under HiWish program. The location is the Casius quadrangle.
• 
  Scalloped terrain, as seen by HiRISE under HiWish program. The location is the Casius quadrangle.

• 
  Crater with colorful ejecta, as seen by HiRISE under the HiWish program The ejecta represents samples of material from underground. Craters allow us to study underlying material.
• 
  Crater with colorful ejecta, as seen by HiRISE The ejecta represents samples of material from underground. Craters allow us to study underlying material.

A pedestal crater is a crater with its ejecta sitting above the surrounding terrain and thereby forming a raised platform (like a pedestal). They form when an impact crater ejects material which forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions.^{[73][74][75][76]}

• 
  Pedestal crater, as seen by HiRISE under HiWish program. Top layer has protected the lower material from being eroded. The location is Casius quadrangle.
• 
  Pedestal crater, as seen by HiRISE under HiWish program. Location is Hellas quadrangle.
• 
  Pedestal crater, as seen by HiRISE under HiWish program. Location is Casius quadrangle.
• 
  Pedestal crater, as seen by HiRISE under HiWish program. Location is Cebrenia quadrangle.

Ring mold craters are believed to be formed from asteroid impacts into ground that has an underlying layer of ice. The impact produces an rebound of the ice layer to form a "ring-mold" shape.

Another, later idea, for their formation suggests that the impacting body goes through layers of different densities. Later, erosion could have helped shape them. It was thought that ring-mold craters could only exist in areas with large amounts of ground ice. However, with more extensive analysis of larger areas, it was found the ring mold craters are sometimes formed where there is not as much ice underground.^{[77] [78]}

• 
  Ring mold craters of various sizes on floor of a crater, as seen by HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.
• 
  Wide view of a field of ring mold craters, as seen by HiRISE under HiWish program
• 
  Close view of ring mold crater, as seen by HiRISE under HiWish program. Note: this is an enlargement of the previous image of a field of ring mold craters.

• 
  Wide view of ring-mold craters on floor of larger crater, as seen by HiRISE under HiWish program
• 
  Ring-mold craters, as seen by HiRISE under HiWish program
• 
  Close view of ring-mold craters and brain terrain, as seen by HiRISE under HiWish program

• 
  Pedestal crater with boulders along rim. Such craters are called "halo craters".^[79] Picture taken with HiRISE under HiWish program.
• 
  Close view of boulders on lower left of crater rim Box is the size of a football field, so boulders are roughly the size of cars or small houses. Picture taken with HiRISE under HiWish program.
• 
  Close view of boulders along crater rim Boulders are roughly the size of cars or small houses. Picture taken with HiRISE under HiWish program.

• 
  Boulders, as seen by HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.
• 
  Boulder and boulder tracks, as seen by HiRISE under HiWish program. The arrow shows a boulder that has made a track in the sand as it rolled down dune. Location is Mare Boreum quadrangle.
• 
  Boulders and tracks, as seen by HiRISE under HiWish program. The arrows show a boulders that have produced a track by rolling down dune. Location is Mare Boreum quadrangle.
• 
  Boulders and their tracks from rolling down a slope, as seen by HiRISE under HiWish program. Arrows show two boulders at the end of their tracks. Location is Arabia quadrangle.

Dust devil tracks can be very pretty. They are caused by giant dust devils removing bright colored dust from the Martian surface; thereby exposing a dark layer. Dust devils on Mars have been photographed both from the ground and high overhead from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.^[80] The pattern of the tracks has been shown to change every few months.^[81] A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 metres (2,300 ft) and last at least 26 minutes.^[82]

• 
  Dust devil tracks, as seen by HiRISE under HiWish program
• 
  Dust devil tracks, as seen by HiRISE under HiWish program
• 
  Layers in Danielson Crater with dust devil tracks at the top of the picture, as seen by HiRISE under HiWish program. Location is Oxia Palus quadrangle.
• 
  Wide view of dust devil tracks, as seen by HiRISE under HiWish program. Location is the Phaethontis quadrangle.

Yardangs are common in some regions on Mars, especially in what is called the "Medusae Fossae Formation". This formation is found in the Amazonis quadrangle and near the equator.^[83] They are formed by the action of wind on sand sized particles; hence they often point in the direction that the winds were blowing when they were formed.^[84] Because they exhibit very few impact craters they are believed to be relatively young.^[85]

• 
  Yardangs, as seen by HiRISE under HiWish program. Location is near Gordii Dorsum in the Amazonis quadrangle. These yardangs are in the upper member of the Medusae Fossae Formation.
• 
  Yardangs, as seen by HiRISE under HiWish program. Location is near Gordii Dorsum in the Amazonis quadrangle. Note: this is an enlargement of previous image.
• 
  Yardangs, as seen by HiRISE under HiWish program. Location is near Gordii Dorsum in the Amazonis quadrangle. Note: this is an enlargement of previous image.

• 
  Yardangs formed in light-toned material and surrounded by dark, volcanic basalt sand, as seen by HiRISE under HiWish program. Loacation is Margaritifer Sinus quadrangle.
• 
  Close-up image of yardangs, as seen by HiRISE under HiWish program. Arrows point to transverse aeolian ridges (TARs), a type of dune. Note this is an enlargement of the previous image from HiRISE.

At certain times in the Martian, dark eruptions of gas and dust occur. Wind often blows the material into a fan or a tail-like shape. During the winter, much frost accumulates. It freezes out directly onto the surface of the permanent polar cap, which is made of water ice covered with layers of dust and sand. The deposit begins as a layer of dusty CO₂ frost. Over the winter, it recrystallizes and becomes denser. The dust and sand particles caught in the frost slowly sink. By the time temperatures rise in the spring, the frost layer has become a slab of semi-transparent ice about 3 feet thick, lying on a substrate of dark sand and dust. This dark material absorbs light and causes the ice to sublimate (turn directly into a gas). Eventually much gas accumulates and becomes pressurized. When it finds a weak spot, the gas escapes and blows out the dust. Speeds can reach 100 miles per hour.^[86] Calculations show that the plumes are 20–80 meters high.^[87][88] Dark channels can sometimes be seen; they are called "spiders".^[89][90][91] The surface appears covered with dark spots when this process is occurring.^[86][92]

Many ideas have been advanced to explain these features.^{[93][94][95][96][97][98] [99]} These features can be seen in some of the pictures below.

• 
  Wide view of plumes, as seen by HiRISE under HiWish program. Many of the plumes show spiders when enlarged.
• 
  Plumes, as seen by HiRISE under HiWish program. Arrow shows a double plume. This may have been because of shifting winds.
• 
  Long plume, as seen by HiRISE under HiWish program
• 
  Spiders, as seen by HiRISE under HiWish program
• 
  Plumes and spiders, as seen by HiRISE under HiWish program
• 
  Plumes and spiders, as seen by HiRISE under HiWish program
• 
  Plumes and spiders, as seen by HiRISE under HiWish program
• 
  Wide view of plumes and spiders, as seen by HiRISE under HiWish program
• 
  Plumes and spiders, as seen by HiRISE under HiWish program

Remnants of a 50–100 meter thick mantling, called the upper plains unit, has been discovered in the mid-latitudes of Mars. First investigated in the Deuteronilus Mensae (Ismenius Lacus quadrangle) region, but it occurs in other places as well. The remnants consist of sets of dipping layers in craters and along mesas.^[100] Sets of dipping layers may be of various sizes and shapes—some look like Aztec pyramids from Central America. Dipping layers are common in some regions of Mars. They may be the remains of mantle layers. Another idea for their origin was presented at 55th LPSC (2024) by an international team of researchers. They suggest that the layers are from past ice sheets.^[101]

• 
  Layered structure in crater that is probably what is left of a layered unit that once covered a much larger area. Material for this unit fell from the sky as ice-coated dust. The picture was taken by HiRISE, under the HiWish program. Picture is from Hellas quadrangle.

• 
  Tilted layers, as seen by HiRISE under HiWish program. Location is Hellas quadrangle.
• 
  Tilted layers, as seen by HiRISE under HiWish program. Location is Hellas quadrangle.
• 
  Tilted layers, as seen by HiRISE under HiWish program. Location is Hellas quadrangle.

• 
  Dipping layers, as seen by HiRISE under HiWish program
• 
  Layered features in crater, as seen by HiRISE under HiWish program
• 
  Layered structures, as seen by HiRISE under HiWish program
• 
  Close view of dipping layers along a mesa wall, as seen by HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.
• 
  Close view of dipping layers in Ismenius Lacus quadrangle, as seen by HiRISE under HiWish program
• 
  Wide view of dipping layers in Ismenius Lacus quadrangle, as seen by HiRISE under HiWish program. Gullies are also visible at the bottom of the image.

This unit also degrades into brain terrain. Brain terrain is a region of maze-like ridges 3–5 meters high. Some ridges may consist of an ice core, so they may be sources of water for future colonists.

• 
  Brain terrain, as seen by HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.
• 
  Layered features and brain terrain, as seen by HiRISE under HiWish program. The upper plains unit often changes into brain terrain.
• 
  Brain terrain is forming from the breakdown of upper plains unit, as seen by HiRISE under HiWish program. Arrow points to a place where fractures are forming that will turn into brain terrain.
• 
  Brain terrain is forming from the breakdown of upper plains unit, as seen by HiRISE under HiWish program. Arrow points to a place where fractures are forming that will turn into brain terrain.

• 
  Wide view of brain terrain being formed, as seen by HiRISE under HiWish program
• 
  Brain terrain being formed, as seen by HiRISE under HiWish program. Note: this is an enlargement of the previous image using HiView. Arrows indicate spots where brain terrain is beginning to form.
• 
  Brain terrain being formed, as seen by HiRISE under HiWish program. Note: this is an enlargement of a previous image using HiView. Arrows indicate spots where brain terrain is beginning to form.
• 
  Brain terrain being formed, as seen by HiRISE under HiWish program. Note: this is an enlargement of a previous image using HiView.
• 
  Brain terrain being formed, as seen by HiRISE under HiWish program. Note: this is an enlargement of a previous image using HiView.
• 
  Open and closed brain terrain with labels, as seen by HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.
• 
  Brain terrain being formed, as seen by HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.

• 
  Wide view of brain terrain being formed, as seen by HiRISE under HiWish program
• 
  Brain terrain being formed, as seen by HiRISE under HiWish program. Note: this is an enlargement of the previous image using HiView.
• 
  Brain terrain being formed, as seen by HiRISE under HiWish program. Note: this is an enlargement of a previous image using HiView.

Some regions of the upper plains unit display large fractures and troughs with raised rims; such regions are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Stress is suggested to initiate the fracture process since ribbed upper plains are common when debris aprons come together or near the edge of debris aprons—such sites would generate compressional stresses. Cracks exposed more surfaces, and consequently more ice in the material sublimates into the planet's thin atmosphere. Eventually, small cracks become large canyons or troughs.

• 
  Well developed ribbed upper plains material. These start with small cracks that expand as ice sublimates from the surfaces of the crack. Picture was taken with HiRISE under HiWish program.
• 
  Dipping layers, as seen by HiRISE under HiWish program. Also, Ribbed Upper plains material is visible in the upper right of the picture. It is forming from the upper plains unit, and in turn is being eroded into brain terrain.

• 
  Wide view showing ribbed terrain and brain terrain, as seen by HiRISE under HiWish program
• 
  Ribbed terrain being formed from upper plains unit, as seen by HiRISE under HiWish program. Formation begins with cracks that enhance sublimation. Box shows the size of football field.

Small cracks often contain small pits and chains of pits; these are thought to be from sublimation of ice in the ground.^[102][103]Large areas of the Martian surface are loaded with ice that is protected by a meters thick layer of dust and other material. However, if cracks appear, a fresh surface will expose ice to the thin atmosphere.^[104][105] In a short time, the ice will disappear into the cold, thin atmosphere in a process called sublimation. Dry ice behaves in a similar fashion on the Earth. On Mars sublimation has been observed when the Phoenix lander uncovered chunks of ice that disappeared in a few days.^[39][106] In addition, HiRISE has seen fresh craters with ice at the bottom. After a time, HiRISE saw the ice deposit disappear.^[107]

The upper plains unit is thought to have fallen from the sky. It drapes various surfaces, as if it fell evenly. As is the case for other mantle deposits, the upper plains unit has layers, is fine-grained, and is ice-rich. It is widespread; it does not seem to have a point source. The surface appearance of some regions of Mars is due to how this unit has degraded. It is a major cause of the surface appearance of lobate debris aprons.^[103]The layering of the upper plains mantling unit and other mantling units are believed to be caused by major changes in the planet's climate. Models predict that the obliquity or tilt of the rotational axis has varied from its present 25 degrees to maybe over 80 degrees over geological time. Periods of high tilt will cause the ice in the polar caps to be redistributed and change the amount of dust in the atmosphere.^{[108][109][110]}

Linear ridge networks are found in various places on Mars in and around craters.^[111] Ridges often appear as mostly straight segments that intersect in a lattice-like manner. They are hundreds of meters long, tens of meters high, and several meters wide. It is thought that impacts created fractures in the surface, these fractures later acted as channels for fluids. Fluids cemented the structures. With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind. Since the ridges occur in locations with clay, these formations could serve as a marker for clay which requires water for its formation. Water here could have supported life.^{[112][113][114]}

• 
  Network of ridges, as seen by HiRISE under HiWish program. Ridges may be formed in various ways.
• 
  Color, close-up of ridges seen in previous image, as seen by HiRISE under HiWish program
• 
  Close-up and color image of linear ridge network, as seen by HiRISE under HiWish program
• 
  More linear ridge networks from same location as previous image, as seen by HiRISE under HiWish program
• 
  Linear ridge networks, as seen by HiRISE under HiWish program. Location is Amazonis quadrangle.
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  Linear ridge network, as seen by HiRISE under HiWish program. Location is Mare Tyrrhenum quadrangle.
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  Linear ridge network, as seen by HiRISE under HiWish program. Location is Casius quadrangle.
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  Wide view of ridge network, as seen by HiRISE under HiWish program. Location is Arcadia quadrangle.
• 
  Close view of ridge networks, as seen by HiRISE under HiWish program. Arrow points to small, straight ridge. Location is Arcadia quadrangle.

• 
  Wide view of network of ridges, as seen by HiRISE under HiWish program. Portions of this image are enlarged in following images.
• 
  Close view of network of ridges, as seen by HiRISE under HiWish program. This is an enlargement of a previous image.
• 
  Close view of network of ridges, as seen by HiRISE under HiWish program. This is an enlargement of a previous image. Box shows the size of a football field.
• 
  Close view of network of ridges, as seen by HiRISE under HiWish program. This is an enlargement of a previous image.
• 
  Close view of ridges, as seen by HiRISE under HiWish program. This is an enlargement of a previous image. A small mesa in the image displays layers.
• 
  Close, color view of network of ridges, as seen by HiRISE under HiWish program. This is an enlargement of a previous image.

• 
  Wide view of large ridge network, as seen by HiRISE under HiWish program
• 
  Close view of ridge network, as seen by HiRISE under HiWish program. Box shows size of football field.
• 
  Close, color view of ridges, as seen by HiRISE under HiWish program

Some places on Mars break up with large fractures that created a terrain with mesas and valleys. Some of these can be quite pretty.

• 
  Wide view of fractured ground, as seen by HiRISE under HiWish program
• 
  Close view of fractured ground, as seen by HiRISE under HiWish program
• 
  Close view of fractured ground, as seen by HiRISE under HiWish program. Box shows size of football field. The boulders are the size of houses.
• 
  Close, color view of fractured ground, as seen by HiRISE under HiWish program

• 
  Mesa, as seen by HiRISE under HiWish program. This may make for a good race around a mesa someday in the far future.

• 
  Mesa with layers, as seen by HiRISE under HiWish program. Location is Mare Acidalium quadrangle.
• 
  Close view of layers in mesa, as seen by HiRISE under HiWish program

• 
  Wide view of layered buttes and small mesas, as seen by HiRISE under HiWish program. Some dark slope streaks are visible. Location is Aeolis quadrangle. Parts of this image are enlarged in next three pictures.
• 
  Layered mesa and mounds with dark slope streaks, as seen by HiRISE under HiWish program
• 
  Close view of layered small mesa with dark slope streak, as seen by HiRISE under HiWish program. Box shows the size of a football field.
• 
  Very close view of individual blocks breaking off layer in a butte, as seen by HiRISE under HiWish program. Blocks have angular shapes. Box shows size of football field.
• 
  Layered mesa, as seen by HiRISE under HiWish program
• 
  Layered mesa, as seen by HiRISE under HiWish program Box is the size of a football field.

• 
  Group of mesas, as seen by HiRISE under HiWish program. Oval box contains mesas that may have moved apart.
• 
  Enlarged view of a group of mesas, as seen by HiRISE under HiWish program. One surface is forming square shapes.
• 
  Mesas breaking up forming straight edges, as seen by HiRISE under HiWish program

There is evidence that volcanoes sometimes erupt under ice, as they do on Earth at times. What seems to happen it that much ice melts, the water escapes, and then the surface cracks and collapses. These exhibit concentric fractures and large pieces of ground that seemed to have been pulled apart.^[115] Sites like this may have recently had held liquid water, hence they may be fruitful places to search for evidence of life.^[116][117]

• 
  Large group of concentric cracks, as seen by HiRISE, under HiWish program. Location is Ismenius Lacus quadrangle. Cracks were formed by a volcano under ice.^[116]
• 
  Tilted layers formed when ground collapsed, as seen by HiRISE, under HiWish program
• 
  Tilted layers formed from ground collapse, as seen by HiRISE, under HiWish program
• 
  Mesas breaking up into blocks, as seen by HiRISE, under HiWish program

In places large fractures break up surfaces. Sometimes straight edges are formed and large cubes are created by the fractures.

• 
  Wide view of mesas that are forming fractures, as seen by HiRISE under HiWish program
• 
  Enlarged view of a part of previous image, as seen by HiRISE under HiWish program. The rectangle represents the size of a football field.
• 
  Close-up of blocks being formed, as seen by HiRISE under HiWish program
• 
  Close-up of blocks being formed, as seen by HiRISE under HiWish program. The rectangle represents the size of a football field, so blocks are the size of buildings.
• 
  Close-up of blocks being formed, as seen by HiRISE under HiWish program. Many long fractures are visible on the surface.
• 
  Surface breaking up, as seen by HiRISE under HiWish program. Near the top the surface is eroding into brain terrain.
• 
  Wide view showing light-toned feature that is breaking into blocks, as seen by HiRISE under HiWish program
• 
  Close view showing blocks being formed, as seen by HiRISE under HiWish program. Note: this is an enlargement of the previous image. Box represents size of football field.

• 
  Lava flow in Tharsis quadrangle, as seen by HiRISE under HiWish program
• 
  Close-up of lava flow with labels, as seen by HiRISE under HiWish program. Note: this is an enlargement of the previous image of lava flows.
• 
  Lava flows with older and younger flows labeled, as seen by HiRISE under HiWish program
• 
  Edge of lava flow, as seen by HiRISE under HiWish program. Location is Solis Planum in Phoenicis Lacus quadrangle.
• 
  Wide view of streamlined shape and rafts of lava, as seen by HiRISE under HiWish program
• 
  Close view of lava rafts from previous image, as seen by HiRISE under HiWish program

So-called "rootless cones" are caused by explosions of lava with ground ice under the flow.^[118][119] The ice melts and turns into a vapor that expands in an explosion that produces a cone or ring. Featureslike these are found in Iceland, when lavas cover water-saturated substrates.^{[120][118][121]}

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  Wide view of field of rootless cones, as seen by HiRISE under HiWish program. Location is Elysium quadrangle.
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  Close view of rootless cones with tails that suggest lava was moving toward the Southwest over ice-rich ground, as seen by HiRISE under HiWish program
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  Close view of cones with the size of a football field shown, as seen by HiRISE under HiWish program
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  Close view of cones, as seen by HiRISE under HiWish program. These cones probably formed when hot lava flowed over ice-rich ground. The location is the Elysium quadrangle.
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  Rootless Cones, as seen by HiRISE under HiWish program. These group of rings or cones are believed to be caused by lava flowing over water ice or ground containing water ice. The ice quickly changes to steam which blows out a ring or cone. Here the kink in the chain may have been caused by the lava changing direction. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form. The location is the Elysium quadrangle.

Some features look like volcanoes. Some of them may be mud volcanoes where pressurized mud is forced upward forming cones. These features may be places to look for life as they bring to the surface possible life that has been protected from radiation.

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  Large field of cones that may be mud volcanoes, as seen by HiRISE under HiWish program. Location is Mare Acidalium quadrangle.
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  Close-up of possible mud volcanoes, as seen by HiRISE under HiWish program. Note: this is an enlargement of the previous image.

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  Mud volcanoes, as seen by HiRISE under HiWish program. The location is Mare Acidalium quadrangle. There are many mud volcanoes in Mare Acidalium quadrangle.
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  Possible mud volcano, as seen by HiRISE under HiWish program. The location is Mare Acidalium quadrangle.

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  Wide view of field of mud volcanoes, as seen by HiRISE under HiWish program
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  Close view of mud volcanoes, as seen by HiRISE under HiWish program
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  Close view of mud volcanoes and boulders, as seen by HiRISE under HiWish program
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  Close view of mud volcano, as seen by HiRISE. Picture is about 1 km across. This mud volcano has a different color than the surroundings because it consists of material brought up from depth. These structures may be useful to explore for remains of past life since they contain samples that would have been protected from the strong radiation at the surface.

Strange terrain was discovered on parts of the floor of Hellas Planitia. Scientists are not sure of how it formed.

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  Twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program
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  Floor features in Hellas Planitia, as seen by HiRISE under HiWish program
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  Floor features in Hellas Planitia, as seen by HiRISE under HiWish program
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  Close view of groups of ridges on Hellas floor, as seen by HiRISE under HiWish program

Exhumed craters seem to be in the process of being uncovered.^[122] It is believed that they formed, were covered over, and now are being exhumed as material is being eroded. When a crater forms, it will destroy what is under it. In the example below, only part of the crater is visible. if the crater came after the layered feature, it would have removed part of the feature and we would see the entire crater.

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  Wide view of exhumed craters, as seen by HiRISE under HiWish program
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  Close view of exhumed crater, as seen by HiRISE under HiWish program. This crater is and was under a set of dipping layers.

To suggest a location for HiRISE to image visit the site at http://www.uahirise.org/hiwish

In the sign up process you will need to come up with an ID and a password. When you choose a target to be imaged, you have to pick an exact location on a map and write about why the image should be taken. If your suggestion is accepted, it may take 3 months or more to see your image. You will be sent an email telling you about your images. The emails usually arrive on the first Wednesday of the month in the late afternoon.

• Climate of Mars
• Common surface features of Mars
• Geology of Mars
• Glaciers
• Glaciers on Mars
• Barchan
• Groundwater on Mars
• Martian gullies
• Mud volcano
• Linear ridge networks
• Water on Mars
• Yardangs on Mars

• Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
• Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.
• Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM.

• HiRISE images from HiWish Program
• /0:48 Zooming in on Mars with HiRISE images from HiWish program
• Features of Mars with HiRISE under HiWish program Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.
• A trip to Mars with Hubble, Viking, and HiRISE
• Mars through HiRISE under the HiWish program
• Beautiful Mars as seen by HiRISE under HiWish program
• Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention
• Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention
• Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention
• How to Explore Mars without Leaving Your Chair - Jim Secosky - 23rd Annual Mars Society Convention
• Stillman, D., et al. 2017. Characteristics of the numerous and widespread recurring slope lineae (RSL) in Valles Marineris, Mars. Icarus. Volume 285. Pages 195-210

• McEwen, A., et al. 2024. The high-resolution imaging science experiment (HiRISE) in the MRO extended science phases (2009–2023). Icarus. Available online 16 September 2023, 115795. In Press.