Curiosity: Martian Surface Soil Contains Two Percent Water

Sep 27, 2013 by

In five papers published today in the journal Science, scientists using the ChemCam, CheMin instruments, the Alpha Particle X-ray Spectrometer (APXS) and the Sample Analysis at Mars (SAM) suite aboard NASA’s Curiosity Rover team up to describe the Red Planet’s once-volcanic and aquatic history.

NASA's Curiosity Rover. Image credit: NASA / JPL-Caltech / Malin Space Science Systems.

NASA’s Curiosity Rover. Image credit: NASA / JPL-Caltech / Malin Space Science Systems.

The ChemCam instrument showed that the Martian soils consist of two distinct components. In addition to extremely fine-grained particles that seem to be representative of the ubiquitous dust covering the entire planet’s surface like the fine film that collects on the undisturbed surfaces of a long-abandoned home, the ChemCam team discovered coarser-grained particles up to 1 mm in size that reflected the composition of local rocks.

The ChemCam has shown a similar composition to fine-grained dust characterized on other parts of the planet during previous Martian missions. The instrument tested more than 100 targets in a location named Rocknest and found that the dust contained consistent amounts of water regardless of the sampling area.

What’s more, the Curiosity dug into the soils at Rocknest to provide scientists with the opportunity to sample the newly unearthed portion over the course of several Martian days.

The ChemCam instrument measured roughly the same tiny concentration of water – about 2 percent – in the surface soils as it did in the freshly uncovered soil, and the newly excavated area did not dry out over time – as would be expected if moist subsurface material were uncovered.

The water signature may coincide with the tiny amount of ambient humidity in the Red Planet’s arid atmosphere. Multiple observations indicate that the flowing water responsible for shaping and moving the rounded pebbles encountered in the vicinity of the rover landing area has long since been lost to space, though some of it may still exist deep below the surface of the planet at equatorial locations.

Despite the seemingly small measurements of water in the Martian environment, the findings nevertheless are exciting.

“In principle it would be possible for future astronauts to heat the soil to derive water to sustain them,” said Dr Roger Wiens of the ChemCam instrument team, who is a co-author of two Science papers.

The researchers using the SAM instrument suite has found that surface soil on Mars contains about 2 percent water by weight.

“About 2 percent of the soil on the surface of Mars is made up of water, which is a great resource, and interesting scientifically. The sample also released significant carbon dioxide, oxygen and sulfur compounds when heated,” said Dr Laurie Leshin from Rensselaer Polytechnic Institute, a lead author of one Science paper.

The analyses by CheMin and SAM indicate that Mars likely has a volcanic history that shaped the surface of the planet.

The APXS spectrometer provides additional insights into the volcanic diversity on Mars.

The instrument analyzed a rock called Jake Matijevic and found that it is one of the most Earth-like rocks yet seen on Mars. The rock’s enrichment in sodium, giving it a feldspar-rich mineral content, makes it very similar to some rocks erupted on ocean islands on Earth.


Bibliographic information: L. A. Leshin et al. 2013. Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover. Science, vol. 341, no. 6153; doi: 10.1126/science.1238937

P.Y. Meslin et al. 2013. Soil Diversity and Hydration as Observed by ChemCam at Gale Crater, Mars. Science, vol. 341, no. 6153; doi: 10.1126/science.1238670

D. L. Bish et al. 2013. X-ray Diffraction Results from Mars Science Laboratory: Mineralogy of Rocknest at Gale Crater. Science, vol. 341, no. 6153; doi: 10.1126/science.1238932

D. F. Blake et al. 2013. Curiosity at Gale Crater, Mars: Characterization and Analysis of the Rocknest Sand Shadow. Science, vol. 341, no. 6153; doi: 10.1126/science.1239505

E. M. Stolper et al. 2013. The Petrochemistry of Jake_M: A Martian Mugearite. Science, vol. 341, no. 6153; doi: 10.1126/science.1239463