The document discusses several active geological processes observed on Mars including slope streaks, gully formation, recurring slope lineae (RSL), dust avalanches, and impacts. Slope streaks are believed to form from downslope movement of dry sand or dust in an almost fluid-like manner, exposing darker material underneath. Gullies are thought to form from seasonal frost or from the sublimation of dry ice blocks, which can slide down dune slopes. RSL are dark flows on steep rocky slopes that are correlated with seasonal frost. Dust avalanches and small asteroid impacts continue to shape Mars' surface and may trigger slope streaks. HiRISE images provide evidence that Mars remains an active planet, with subtle changes

1. • Mechanism of formation & triggering is debated; may
form by similar processes as dust avalanches.
• Most commonly believed to form by down-slope movement
of extremely dry sand or very fine-grained dust in an
almost fluid-like manner (analogous to a terrestrial snow
avalanche) exposing darker underlying material.
• Darkest slope streaks are youngest & can be seen to
cross-cut & lie on top of older & lighter-toned streaks.
• Lighter-toned streaks are streaks that are lightening
with time as new dust is deposited on their surface.
• Upto a few hundred meters wide & several km long.
• Most dramatic & rare event observed along steep cliffs
in North Polar Layered Deposits and steep slopes of dunes
& craters, happening in Martian summer.
• Triggering mechanism may be defrosting, meteoric impact or
freeze & thaw in cracks of loose material along steep slopes.
• The thin atmosphere of Mars, which is mostly made up of CO2 , is quite
active with its sand storms & dust devils.
• Fading of slope streaks and rover tracks over long durations show week
depositional process.
• Following images show dome dunes in the Endeavour crater rapidly
migrated (4–12 m/Mars year) in just 2 Martian seasons; some of the fastest
translating Martian dunes detected to date.
• RSL are dark flows up to a few meters wide on steep, rocky slopes.
• Known to be abundant in equatorial regions, especially deep in
Valles Marineris.
• Follow the sun: active on N-facing slopes when the Sun is to the
north; active on S-facing slopes when the Sun is to the south.
• Important candidate for finding liquid water on Mars.
• Show depositional fans / aprons at their bases, unlike slope
streaks.
• Very slow activity; changes in at least 1 gully observed at about 15%
MRO/HiRISE monitoring sites in southern hemisphere over a period of ~2
Martian years.
• Changes in gullies include channel incision & substantial mass
movements, which are thought to be driven by mass movements.
• Not a candidate for liquid water activity as the gullies only active in
winters; thus seasonally controlled & correlated with seasonal frost.
• Mars is bombarded by
around 200 small asteroids or
bits of comets per year
forming craters at least 4 m
across.
• New craters are identified by
their darker ejecta as
compared to surroundings.
• One of the triggering
mechanisms for avalanches
which cause the slope streaks.
It's easy to think of Mars as static, unchanging - a "geologically dead" planet, as is often mentioned. The first images taken at close approach to Martian surface came to us in 1965 from Mariner 4. Since
then, many more images have revealed features that, except for becoming clearer and more detailed as cameras improve, seem much the same as they did more than 40 years ago. But while this apparent
fixedness of the Martian surface might be true when compared to Earth, a closer look shows that slowly & on small scales, Mars remakes its image even today. HiRISE, onboard NASA’s MRO, with its ability
to see meter-sized features, is one of the best suited instruments to capture these changes. The closer we look at Mars, the more fascinating processes- active in both past & present- we find to study.
Impacts
Aeolian Activities
Slope Streaks
Gully Formation by Frost
Recurring Slope Lineae (RSL)
Active Mars
A Glimpse at the Active Geological Processes on the Planet Mars
Prathamesh S. Pawar
S. P. Pune University, PuneIntroduction
Dust Avalanches
2010-Oct-04 2010-Aug-21
• Observed in polar regions.
• When warmed, dry ice blocks sublimate (go directly
from solid to gas), rather than melt. This creates a
cushion of gas beneath the block that makes it very easy
for the block to slide or roll down the dune slope, carving
out a shallow trough.
• Over many winters, downhill motion of broken dry ice
blocks can perhaps form the large linear gullies (up to 2km
long!) seen on Martian dunes.
Gully Formation by Dry Ice Blocks
Reference and Images: NASA/JPL/University of Arizona: http://www.uahirise.org/