Update from Curiosity: Gale Crater might be drier than expected

Sep 28, 2012
Credit: Russian Federal Space Agency/NASA.JPL-Caltech

(Phys.org)—Preliminary data from the Curiosity Mars Science Laboratory, presented at the European Planetary Science Conference on 28 September, indicate that the Gale Crater landing site might be drier than expected.

The Curiosity rover is designed to carry out research into whether Mars was ever able to support life, and a key element of this search is the hunt for water. Although Mars has many features on its surface that suggest a distant past in which the planet had abundant in the form of rivers and lakes, the only water known to be abundant on Mars today is frozen, embedded in the soil, and in large ice caps at both poles.

The Dynamic Albedo of Neutrons (DAN) instrument on board Curiosity is designed to detect the location and abundance of water thanks to the way hydrogen (one of water's components) reflects neutrons. When neutrons hit heavy particles, they bounce off with little loss in energy, but when they hit (which are much lighter and have approximately the same mass as neutrons), they lose half of their energy.

The DAN instrument works by firing a pulse of neutrons at the ground beneath the rover and detecting the way it is reflected. The intensity of the reflection depends on the proportion of water in the ground, while the time the pulse takes to reach the detector is a function of the depth at which the water is located.

This image of NASA's Curiosity rover shows the location of the two components of the Dynamic Albedo of Neutrons instrument. The neutron generator is mounted on the right hip (visible in this view), and the detectors are on the opposite hip. Credit: NASA/JPL-Caltech

"The prediction based on previous measurements using the was that the soil in Gale Crater would be around 6% water. But the preliminary results from Curiosity show only a fraction of this," said Maxim Mokrousov (Russian Space Research Institute), the lead designer of the instrument.

One possible explanation of the lies in the variability of across the surface of Mars. There are large-scale variations, with in particular having high abundances of water, but also substantial local differences even within individual regions on Mars.

The Mars Odyssey spacecraft is only able to measure water abundance for an area around 300 by 300 kilometres – it cannot make high resolution maps. It may therefore be that Odyssey's figure for Gale Crater is an accurate (but somewhat misleading) average of significantly varying hydrogen abundances in different parts the crater.

Indeed, over the small distance that the rover has already covered, DAN has observed variations in the detector counting rates that may indicate different levels of hydrogen in the ground, hinting that this is likely to be the case.

Curiosity's ability to probe the water content in the martian soil in specific locations, rather than averages of broad regions, allows for a far more precise and detailed understanding of the distribution of water ice on Mars.

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User comments : 3

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ValeriaT
1 / 5 (2) Sep 29, 2012
The physorg isn't supposed to become another reddit or digg site for fat lazy kids, where people are doing nothing else but attempts for silly semantic jokes. If you have nothing to say about subject, don't say it here.
javjav
not rated yet Sep 29, 2012
Intetstingly, if could also mean that there is a really wet subsurface area somewhere in the crater. For example, if there is only a 1% water around you after measuring half of the crater,but you know the average is 6%, there nust be 11% water in the other half., and probably even more concentrated in one small area
Jitterbewegung
1 / 5 (1) Sep 29, 2012
Can't they test that hypothesis of yours in a desert with an oasis here on Earth?
They could even get a direction of the source out of the variations.
Maybe there is a spring evaporating on Mars.

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