Sky & Telescope - April 2024 - 6

NASA / JPL-CALTECH / MSSS / IRAP
FROM OUR READERS
"
Monica Young replies: You pose a
good question! The study authors
address this in more detail in their paper,
noting that the surface on which they see
these mud cracks is resistant to erosion:
" The present appearance of the sulfatebearing
ridges is probably not the original
configuration of these features. More plausibly,
they started out as evapoconcentration
deposits focused on initially formed
cracks that then evolved over a longer history
of drying cycles and burial diagenesis
(https://is.gd/MarsCyclesFig3).
" They are now exposed as erosionDusty
Martian Dilemma
I'm looking at the image of the dustcovered
Insight Mars Lander on page 6
of the December issue, and I'm wondering:
What if that lander had had a little
helicopter to partner with? Couldn't the
helicopter utilize its downwash to dust
off the larger craft? Then there could be
another role for Mars-based helicopters
other than wayfinding. The technology
doesn't need to be invented. It is already
there and can be tested anytime the
technicians have a spare moment. This
would elevate Mars-based helicopters
from nice to essential.
Arnold Miller
Lynnwood, Washington
"
Camille M. Carlisle replies: I don't
know whether a small helicopter
could create a forceful enough downwash
in the thin Martian air to clean off solar
panels - and to be honest, I doubt mission
planners would be willing to test the idea.
The Ingenuity and Perseverance teams
have been careful to keep the two explorers
apart, to avoid any possibility of collision
and damage. There's also the question of
whether the downwash's effect would be
positive or negative - it might kick more
dust onto solar panels.
A study from 2022 found that Ingenuity
kicks up dust when a few meters above the
ground (https://is.gd/IngenuityDust). So
for any chance of cleaning off a lander or
rover, navigators would have to bring the
flyer within perhaps 10 feet of a solar panel
6
APRIL 2024 * SKY & TELESCOPE
p NASA's Curiosity rover discovered mud
cracks on Mars in 2021. The polygonal shapes
depicted here formed after many wet-dry
climate cycles.
- a sure way to raise the blood pressure
of rover drivers, who are watching from
another planet and with several minutes of
signal delay. Those dust clouds might also
keep circulating and rain dust back down
on the panels.
Even if the panels are spick-and-span,
there's still the matter of dust in the atmosphere.
Ingenuity itself has had trouble
charging its battery when dust levels are
high: https://is.gd/IngenuityComs.
" What Mud Cracks Mean for Life on
Mars " by Colin Stuart (S&T: Dec. 2023,
p. 8) was a very interesting article. I
know that the implication for extraterrestrial
life probabilities was the main
point, but I wonder what processes
allowed the soft soil features to last for
billions of years intact?
Shouldn't they have been eroded by
the frequent sandstorms on Mars after
the wet-dry cycles had ceased? Though
I'm not an expert, preserved ancient soil
features on Earth are quickly buried and
hardened into sandstone, except maybe
in caves or under other special circumstances.
When the overlying layers are
themselves eroded, they become visible,
or they are found during excavation.
Steven Bernstein
Jackson, New Jersey
resistant polygonal ridges owing to their
higher degree of cementation relative to
the host bedrock, and an early bias of
surface salt precipitation in original mudcrack
polygons. "
Page 6 of the December 2023 issue has a
photo of the dust-occluded Insight Mars
Lander. On page 8 of the same issue is
a photo of multi-billion-year-old mud
cracks that appear to be free of dust. Is
there anything to be gleaned from this
beyond whether dust accretes more rapidly
in some areas than in others?
George Nehls
La Crosse, Wisconsin
Monica Young replies: Thanks for
writing in. We asked your question
of William Rapin (Research Institute
in Astrophysics and Planetary Science,
France), who published the results on the
mud cracks on Mars (S&T: Dec. 2023, p.
8), and he agrees with your statement:
" There are indeed variations in how dust is
deposited on Mars. At a global scale, we
have traced dust cover using reflectance
spectroscopy.
"
" The Mars Global Surveyor's Thermal
Emission Spectrometer provides a 'dust
cover index' for example, and it shows
that there are clear regions with elevated
dust deposition rate, like where Insight
is, that act as dust pits, and others with
enough wind to clear rock exposures. "
Curiosity's mud cracks are visible due
in part to luck, he adds: " They are preserved
within a sedimentary rock layer that
is exposed nicely, and luckily, in an area
that is accessible to the rover and indeed
not particularly dust covered. "
https://www.is.gd/MarsCyclesFig3 https://www.is.gd/IngenuityComs https://www.is.gd/IngenuityDust
Sky & Telescope - April 2024

Table of Contents for the Digital Edition of Sky & Telescope - April 2024
