Liquid brine on Mars seems confirmed
From time to time, brine seems to flow on Mars. Scientists say that after extensive study of spectrometer measurements of dark stripes in Martian craters. These stripes visible on high-resolution photos are the so-called ‘Recurring Slope Lineae’ or RSL.
The suspicion of the existence of liquid water on Mars as a result of the dark stripes had been there for some time, reported de Volkskrant in February 2014. The RSL that can occasionally be seen on the inner walls of Mars craters in photos of the Mars Reconnaissance Orbiter, or MRO, now seem to be actually caused by flowing brine. The MRO is a NASA satellite located approximately 370 kilometers from Mars.
Determining whether it was actually brine or something else is very difficult because the ‘streams’ on Mars are between 50 centimeters and 5 meters wide. This makes them too narrow for the much coarser resolution at which the spectrometer on board the MRO takes its measurements at that distance, about 20 meters per pixel. In order to find out what the dark stripes consist of, the researchers of this study developed a new way of using spectrometry to find out what the RSL consist of. With the method, scientists from NASA, among others, were able to find out that there are minerals in the RSL that consist of hydrates of salts, or salts surrounded by water molecules. The specific characteristics for the presence of those salts could not be found in the immediate vicinity.
The RSL are created annually on slopes that are heated by the sun for a long time. After a while they disappear again, something that has been captured for several years by the HiRISE camera on board the MRO. The temperatures at the places where the RSL are formed are then between -23 and 0°C. Water with a lot of salts dissolved in it has a lower freezing point than regular water, so it can become liquid at those temperatures.
CRISM – Spectrometer
Also on board the MRO is a spectrometer, the Compact Reconnaissance Imaging Spectrometer for Mars, also known as the CRISM. The spectrometer can detect wavelengths between the near infrared and the visible electromagnetic spectrum. In this way, CRISM can determine the composition of materials that occur in the Martian soil. The HiRISE camera can detect 30 centimeters per pixel from 300 kilometers, while the CRISM can capture 18.4 meters per pixel at 300 kilometers.
Since Sunday, there has been much speculation about what NASA would come out with under the heading ‘NASA to announce Mars Mystery Solved’. Following a document that ‘leaked’ before a congress of the European Planetary Science Congress, it was suspected that it was the presence of running water. Ultimately, it remains unclear where the water comes from. It may be from the frozen subsurface, but the presence of ice just below the surface in those places on Mars – around the equator – seems highly unlikely. It could be that water is attracted from the atmosphere by hygroscopic salts that attract water. With the latter one can think of a stock cube that has become completely moist after a while. Another option could be a local deep underground water reservoir, but that doesn’t seem likely.
While the existence of brine seems to be confirmed, that doesn’t mean life could exist on the planet in these conditions, even in the form of extremophiles. This is due to the direct influence of space, such as cosmic rays and direct UV radiation through the very thin atmosphere. There is also no magnetic field such as on Earth that protects against radiation, although there are magnetic fields.
NASA indicated at its press conference that the Mars rover Curiosity is relatively close by, but that they are afraid to let it go there because of possible contamination with terrestrial organisms, even though all the carts going into space have been completely sterilized.