is a term used in astrogeology
to refer to "a deep, elongated,
steep-sided depression". The plural is chasmata
Chasma on Mars.
images of some of the major Chasma of Mars. The map shows their
relative locations. Some of the details aboput Chasma are described
Interior layered deposits and sulfate
Parts of the floor of Candor Chasma contains layered deposits that
have been termed interior layered deposits (ILD's). These layers
may have formed when the whole area was a giant lake.Some places on
Mars contain hydrated sulfate
Sulfate formation involves the presence of water. The European Space
Agency's Mars Express found
evidence of perhaps epsomite and kieserite.
Scientists want to visit these
areas with robotic rovers.
Images of rocks in the canyon walls almost always show layers. Some
layers appear tougher than others. In the image below of Ganges Chasma Layers, as seen by HiRISE,
one can see that the upper, light-toned deposits are eroding much
faster than the lower darker layers.
Some cliffs on Mars
show a few darker layers standing out and often breaking into large
pieces; these are thought to be hard volcanic rock instead of soft
ash deposits. An example of hard layers is shown below in the
picture of layers in the canyon wall in Coprates, as seen by
Mars Global Surveyor
of its closeness to the Tharsis volcanic region, the rock layers
may be made of layer after layer of lava
probably mixed with deposits of volcanic ash that fell out of the
air following big eruptions. It is likely the rock strata in the
walls preserve a long geological history of Mars. Dark layers may
be due to dark lava flows. The dark volcanic rock basalt
is common on Mars. However, light-toned
deposits may have resulted from rivers, lakes, volcanic ash, or
wind blown deposits of sand or dust. The Mars Rovers
found light-toned rocks to contain
. Probably having been formed in
water, sulfate deposits are of great interest to scientists because
they may contain traces of ancient life.
Hebes Chasma and hydrated deposits
Hebes Chasma, a large enclosed valley, may have once held water.
Hydrated minerals have been found there. It is thought that
large-scale underground springs of groundwater at different times
burst to the sufrace to form deposits called Light Toned Deposits
(LTD's). Some suggest present or fossilized life forms may be found
there because the deposits are relatively young.
Image:Coprates map.JPG|Map of Coprates
quadrangle showing details of Valles Marineris, the largest canyon system in the solar
Some of the canyons may have once been filled with
water. The map shows the locations of a number of major
Image:Candor Chasm in Coprates.JPG|False
color image of Candor
Chasma showing locations of hydrated sulfate deposits, as seen by THEMIS.
Red colors show rocky places. Greens
and blues show sandy, dusty areas.
Image:Melas Chasma.JPG|Melas Chasma, as seen by THEMIS.
Click on image to see relationship of Melas to other
Image:Cliff in Candor Chasma.JPG|Cliff in
Chasma Plateau, as seen by THEMIS.
Click on image to see relationship
with other features in Coprates quadrangle.
Image:Ganges Chasma.JPG|Cliff in northern
wall of Ganges
Chasma, as seen by THEMIS.
Click on image to see realtionship with other features in the
Image:Ophir Chasma Wall.JPG|Ophir
Wall, as seen by HiRISE
Image:Ius Chasma.JPG|Ius Chasma
, as seen
. Click on image to see
Image:Tithonium Chasma Layers.JPG|Tithonium Chasma
Layers, as seen by
Image:Ganges Chasma Layers.JPG|Ganges Chasma Layers, as seen by HiRISE.
- USGS Astrogeology: Gazetteer of Planetary
Nomenclature - Feature Types
- http:www.universetoday.com/2008/12/11/Groundwater May Have
Played Important Role in Shaping Mars