Rocks on Floor of Jezero Crater, Mars, Show Signs of Sustained Interactions
with Water
Portland, Ore., USA: Since the Perseverance rover landed in Jezero
crater on Mars in February, the rover and its team of scientists back on
Earth have been hard at work exploring the floor of the crater that once
held an ancient lake. Perseverance and the Mars 2020 mission are looking
for signs of ancient life on Mars and preparing a returnable cache of
samples for later analyses on Earth.
Katie Stack Morgan is the Mars 2020 Deputy Project Scientist and a research
scientist at NASA’s Jet Propulsion Laboratory (JPL), and will be providing
an
update on early results
on the Mars 2020 rover mission on Sunday, 10 Oct., at the Geological
Society of America’s Connects 2021 annual meeting in Portland, Oregon.
With Perseverance’s high-tech suite of on-board instruments, the scientific
team has been analyzing the rocks of the crater floor, interpreted for now
as igneous rocks, presumably a volcanic lava flow.
“The idea that this could be a volcanic rock was really appealing to us
from a sample return perspective because igneous rocks are great for
getting accurate age dates. Jezero was one of the few ancient crater lake
sites on Mars that seemed to have both incredible sedimentary deposits as
well as volcanic deposits that could help us construct the geologic time
scale of Mars,” said Stack Morgan.
The lake system and rivers that drained into Jezero crater were likely
active around 3.8–3.6 billion years ago, but the ability to directly date
the age of the rocks in laboratories on Earth will provide the first
definitive insight into the window of time that Mars may have been a
habitable planet.
Using Perseverance’s abrasion tool—which scratches the top surface of the
rock to reveal the rock and its textures—the team discovered that the
crater floor seems to be composed of coarser-grained igneous minerals, and
there are also a variety of salts in the rocks. Observations suggest that
water caused extensive weathering and alteration of the crater floor,
meaning that the rocks were subjected to water for a significant duration
of time.
After using its on-board tools to analyze characteristics of the crater
floor, the next phase was for Perseverance to collect a rock sample using
its drill feature. However, after Perseverance completed its first attempt
at drilling, the core sample tube came up empty.
“We spent a couple of days looking around the rover thinking that the core
might have fallen out of the bit. Then we looked back down the drill hole
thinking it might never have made it out of the hole. All these searches
turned up empty. In the end we concluded that the core was pulverized
during drilling,” said Stack Morgan.
The rock likely became so altered and weakened from interactions with water
that the vibrations and strength from the Perseverance drill pulverized the
sample.
Scientists then targeted another rock that appeared more resistant to
weathering, and Perseverance was able to successfully collect two core
samples—the first in its sample collection. Perseverance’s cache of samples
will be part of a multi-spacecraft handoff, still in development, that will
hopefully be returned to Earth in the early 2030s. From there, scientists
in laboratories on Earth will date and analyze the rocks to see if there
might be any signs of ancient Martian life.
“The rocks of the crater floor were not originally envisioned as the prime
astrobiology target of the mission, but Mars always surprises us when we
look up close. We are excited to find that even these rocks have
experienced sustained interaction with water and could have been habitable
for ancient martian microbes,” said Stack Morgan.
Session 14: T117. Perseverance at Jezero Crater—Characterizing an Ancient
Crater Lake Basin on Mars
Paper 14-1: Early results from the Mars 2020 Perseverance rover in Jezero
Crater, Mars
https://gsa.confex.com/gsa/2021AM/meetingapp.cgi/Paper/367543
Sunday, 10 Oct., 8–8:15 a.m., Oregon Convention Center, Portland Ballroom
256 (Hybrid Room)
Contact: Kathryn Stack Morgan, kathryn.m.stack@jpl.nasa.gov
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