Free Astronomy Magazine November-December 2015

PLANETOLOGY consequently if the liquid generating them is water-based, this must necessarily be mixed with salts having remarkable anti- freeze properties. To show that even today there are rivulets of water flowing on Mars (although briny), the researchers had two possible options: either directly catch it dur- ing its flow, which is unlikely with current- ly available instruments, or detect the pres- ence of certain salts deposited in corre- spondence of the RSL as a result of the evaporation or re-absorption of water by the soil. Since the latter is the most prac- tical option, Ojha and colleagues cross- checked the images of the dark streaks taken by HiRISE with the data on the chem- ical and mineralogical composition of the soil acquired by the CRISM instrument (Compact Reconnaissance Imaging Spectrometer for Mars). The analysis showed the presence of deposits of hydrated salts that geo- graphically coincide with some of the larger RSL; namely, those within the scope of the limited resolving power of the spectrograph (numerous F alse colour im- ages of evolv- ing RSL in Palikir Crater. [Lujendra Ojha et al./Geo- physical Research Letters] The video below shows the evolu- tion of numerous RSL in the equa- torial regions of Mars. [NASA/ JPL/University of Arizona, Alfred S. McEwen]