![]() “The occurrence of recurring slope lineae in these canyons is much more widespread than previously recognised.” “There are so many of them, it’s hard to keep track,” said Matthew Chojnacki of the University of Arizona, and lead author of the study published in the Journal of Geophysical Research: Planets. ![]() The number of individual streaks in each site ranges from a few to more than 1,000. Sites investigated include canyon ridges and isolated peaks – places where it is unlikely the streaks come from underground water reaching the surface. And while the work does not come to definite conclusions about the cause of the phenomenon, it does tend to support previous theories. Now, in a new study, scientists, also using MRO data, have investigated thousands of RSLs in the same region. This suggested that water, even if extremely briny, still flowed in certain seasons, on Mars. They appear during warm weather and disappear in winter.ĭata from the MRO confirmed last year the presence of hydrated salts at some RSL sites, including in Valles Marineris, near the equator. The RSL are dark lines running down slopes and the sides of canyons. Many believe they are the strongest evidence that liquid water still exists on Mars. So-called Martian recurring slope lineae, or RSL for short, were first discovered in 2011 and have been puzzling scientists ever since. NASA / JPL-Caltech / University of Arizona New clues about liquid water on Mars “The layers in the upper few hundred metres display features that indicate a period of erosion, followed by a period of rapid accumulation that is still occurring today,” said Isaac Smith, the study’s lead author. On one side of this, the layers accumulated more quickly and uniformly than on the other. They identified a boundary in the ice across the north polar cap. These take vertical slices of the polar ice deposits and scientists studied hundreds of these looking for variations in the layers. This retreat and regrowth of polar ice are exactly what is shown in the images from MRO’s Shallow Subsurface Radar (SHARAD). When this cycle reverses, polar ice begins accumulating again, while ice is lost from mid-latitudes. The polar caps retreat, and water vapour forms into ground ice and glaciers at mid-latitudes. On Mars, ice ages occur when the planet’s tilt increases, making the poles warmer than mid-latitudes. The new data gives insights into the movement of ice on the planet that will help scientists improve their modelling of past and future climate changes on the Red Planet. The discovery was published in the journal Science in May. The latest findings tally with previous models that suggest the glaciation ended about 400,000 years ago. Scientists recently decoded a record of the most recent Martian ice age, using radar data from NASA’s Mars Reconnaissance Orbiter (MRO) gathered around the northern polar ice cap. NASA / JPL-Caltech / Sapienza University of Rome Brown (2006), Mars Reconnaissance Orbiter Accelerometer Data, NASA Planetary Data System. Similar aerobraking archives are available for the MGS and MARS Odyssey orbiter missions. Raw MRO accelerometer data are also available within their own folder below the data folder. ![]() ![]() The contents and structure of the TAB files are described within text within those data files. For instance, the data presented in the left figure above are from the L2P306.TAB file located within the P300_399 folder within the Profile folder, while the data presented in the right-side figure above are located in the 元P306.TAB file located in the P300_399 folder located within the Altitude folder. Within both the Profile and Altitude folders a user will find subfolders containing ~100 drag passes of data, with each drag pass consisting of a single ASCII file. The data contained within the MRO Aerobraking PDS archive mroa_0001 are provided in either the Altitude or Profile folders within the data folder. There is also a separate ASCII Altitude file which provides derived density and scale height values at specified altitudes (100 km, 110 km, etc.) for both the inbound and outbound portions of that orbit/drag pass as well as at the periapsis altitude, and 1.26 nanobar pressure level during both the inbound and outbound portions of the orbit/drag pass. For each drag pass (spanning orbits 18 - 445 of the mission) there is an individual ASCII Profile file containing derived density values at 1-second intervals for a time period spanning several hundred seconds centered upon the periapse time.
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