Recurring slope lineae on the cliff walls of Mars’s Newton Crater were imaged by the Mars Reconnaissance Orbiter. (Source: NASA)
Analysis of data gathered by NASA’s Mars Reconnaissance Orbiter found strong evidence for the existence of liquid water on the surface of Mars (1).
It is no mystery that there was once water on Mars. Its impressive array of canyons and riverbeds, including the Valles Marineris, the largest known canyon in the solar system, could only have been carved by liquid surface water. Until recently, the only known remaining water on Mars was thought to be locked away in its polar ice caps. However, these new findings mark the first time that liquid water, albeit in very small quantities, has been confirmed to exist on the Martian surface.
In 2010, undergraduates at the University of Arizona studying Martian geography noticed the existence of small dark streaks along the sides of Mars’s equatorial cliffs, known as recurring slope lineae (2). They appeared to darken and shift during the warmest months, suggesting liquid flow just below the surface. However, as temperatures in the region stay consistently below the freezing point of water, many believed that liquid water could not have been the source (2).
In an attempt to uncover the chemical composition of these streaks, scientists analyzed spectral data gathered from the Mars Reconnaissance Orbiter’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). To account for local variations and noise, the team analyzed images taken of several different regions where lineae were present during the late summers of Mars Year 30 and Mars Year 31 (1).
The results from CRISM strongly suggested the streaks contained a mixture of magnesium perchlorate, sodium perchlorate, and magnesium chlorate. These hydrated salts could only have been deposited by liquid water flows, confirming the existence of liquid water on Mars (1). Furthermore, the existence of perchlorates at such high concentrations is enough to keep water from freezing at summer temperatures recorded in the region (1).
Mars’s present supply of liquid water is exciting news, both for the future of human exploration and for the possibility of alien life. Although the high abundance of perchlorates and salt make this water toxic to all but the most hardy known forms of life and unusable for humans without prior processing, this serves as proof that liquid water exists on the Martian surface (1, 2). It seems that our planetary neighbor may not be as dead as we once thought.
References:
- Ojha, L., Wilhelm, M., Murchie, S., Mcewen, A., Wray, J., Hanley, J., . . . Chojnacki, M. (2015). Corrigendum: Spectral evidence for hydrated salts in recurring slope lineae on Mars. Nature Geoscience, 8(11), 829-832. doi:10.1038/ngeo2546
- NASA/Jet Propulsion Laboratory. (2015, September 28). Liquid water flows on today’s Mars: NASA confirms evidence. ScienceDaily. Retrieved October 3, 2015 from sciencedaily.com/releases/2015/09/150928094114.html