Following Water to Understand Mars' Past and Present
Follow the Water
If water was once present on Mars, did it leave any clues? If there was water, where and when did it occur, and how did it affect the surface? Today on Mars, does water exist only as ice and atmospheric water vapor, or does liquid water occasionally appear on the surface?
The Compact
Reconnaissance Imaging Spectrometer for Mars (CRISM), flying
aboard the Mars Reconnaissance Orbiter, is one of NASA's high-tech detectives seeking traces of past and
present water on the Martian surface. CRISM's
science goals are to:
- Measure the changing amounts of water and other
volatiles in the atmosphere and as polar ices. This helps us understand
the workings of Mars' atmosphere and how it's different from
Earth's [more about Mars' atmosphere and polar ices].
- Map
the geology, composition and layering of surface
features. Most of the surface was formed by volcanism and impact
cratering, but water helped shape the planet's landforms. Some regions
of the planet are covered by sedimentary rock, perhaps formed in past
standing water [more about Mars' geology and how it was shaped by water].
CRISM also has a fourth goal, one that sets the stage for human exploration:
What's the common thread in CRISM's work at Mars? WATER.
When, where, in what form, how much, and for how long. In fact,
the objectives of NASA's whole Mars Exploration Program can be summed up in a phrase – "follow the water" – and shown in
a picture:
Recent Highlights
The "follow the water" theme has echoed through NASA's Mars Exploration
Program since the year 2000. Already, missions following this theme
have made new and important findings about Mars that are changing our
picture of how the planet works:
- The MOC camera on Mars Global Surveyor discovered many thousands of gullies on the planet. Viking images suggested that water flowed in the distant
past, but gullies – which are mostly too small to have been seen by
Viking's less capable cameras – must have formed in the very recent
past. [images of gullies]
- MOC found that vast regions of the planet are
covered by layered rocks that almost certainly formed by sedimentary
processes, primarily by wind or in standing water. [images of Mars' layered rocks]
- MOC has also found that carbon dioxide ice in
the south polar residual cap is evaporating away rapidly. Mars is
undergoing global climate change even as we watch! [more]
- The TES instrument, also on Mars Global Surveyor, has found that several regions of Mars are rich in an iron oxide mineral called hematite. The primary way to form hematite is through interaction with water. [more]
- The gamma ray and neutron spectrometer on Mars Odyssey has found that the near subsurface is rich in water ice – containing 50 percent or more – at high latitudes, even far outside the polar caps. Some equatorial regions also have extra water that is chemically bound up in minerals in the surface. [more]
- The THEMIS camera, also on Mars Odyssey, found
that gullies are concentrated in mid-latitudes in a thin blanket of
dusty material that covers the surface. The gullies may be forming by
the melting of dusty snow that still lingers from a past Martian ice
age. [more]
- MER/Opportunity landed at the largest hematite deposit and has shown conclusively that the hematite formed through ground water interaction with ancient, salty water. Some of the layered rocks at the site that contain hematite also contain up to tens of percent sulfate salts and exhibit structural characteristics of dune fields. The environment may have been similar to temporary desert lakes on Earth. [more]
- MER/Spirit landed in Gusev crater looking for
the sediments of an ancient lake. Spirit, too, has found mineral
evidence for ancient water that altered Mars' rocks. [more]
- The OMEGA instrument on Mars Express found that sulfate-rich rocks like those at the MER/Opportunity landing site are also prevalent in several other regions of Mars, especially in the layered rocks inside Valles Marineris. In addition, OMEGA found that parts of the most ancient terrains on Mars have been altered to clay (phyllosilicates). The sulfates and clays (shown as colors on the elevation map below) indicate two different kinds of ancient wet environments. (Image credit Mars Express / OMEGA team.)
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