Last year, the strongest evidence that liquid water flows from time to time on present-day Mars came from the Mars Reconnaissance Orbiter (MRO)’s findings.
Last week, a new report was published based on images from the spacecraft. This new study adds clues about seasonal dark streaks on the planet’s surface.
These streaks are called recurring slope lineae, or RSL. They appear when it’s warm and fade when it’s colder. This repeats annually.
In the image below, white arrows point to many seasonal dark streaks.
Credits: NASA/JPL-Caltech/Univ. of Arizona
The most dense population of RSL is found in Valles Marineris. Here, there are thousands of them.
What is Valles Marineris? It’s the biggest canyon in the solar system and is easily seen below.
It is 10 times wider than Earth’s Grand Canyon, significantly longer, and has a much greater depth. Valles Marineris is near the equator of Mars.
A recent publication in the Journal of Geophysical Research: Planets presented findings from observing 41 RSL sites. Many mysteries remain about the possibility of water at these sites. The ridges of canyons and isolated peaks have seasonal dark streaks, but where do they come from?
This is where salts may come in. It’s very unlikely that these warm-season features would be caused by underground water that has reached the surface. What if salts pulled water from the atmosphere?
In some places last year, hydrated salts were found on Mars. When RSL are forming, is water involved?
To better understand this, the co-authors of the study calculated the amount of water needed if the dark streaks are caused by liquid water.
It’s possible that underground water was punctured when impact craters were created. On the walls inside these craters, RSL had been found in the past. Perhaps underground water could cause the dark streaks. Or maybe it is the salt left behind after moisture has evaporated. But researchers don’t know how so much water could be extracted from the atmosphere to produce the amount on the surface that they calculated.
Maybe RSL were formed with a very small amount of liquid water, or maybe they’re completely dry. The images from the spacecraft are clear, but what they show is not yet fully understood.
Among the conclusions of the report was that some RLS may be modifying local slopes. Images have shown the transport of sediment and minor changes in topography.
If water is involved and it’s close to the surface in either liquid or frozen form, it could be important for humans when we are on the red planet. Additionally, since all life we know of needs liquid water to survive, the possibility that it might exist near the surface would greatly impact the search for life.
MRO is helping to uncover secrets held by the red planet. The spacecraft was launched in 2005 to learn about the changing climate, geologic history and possible ability of Mars to harbor life.