November 14, 2019
NASA/Jet Propulsion Laboratory
Scientists with NASA's Mars
2020 rover have discovered what may be one of the best places to look for signs
of ancient life in Jezero Crater, where the rover will land on Feb. 18, 2021.
Scientists with NASA's Mars 2020
rover have discovered what may be one of the best places to look for signs of
ancient life in Jezero Crater, where the rover will land on Feb. 18, 2021.
A paper published in the
journal Icarus identifies distinct deposits of minerals called
carbonates along the inner rim of Jezero, the site of a lake more than 3.5
billion years ago. On Earth, carbonates help form structures that are hardy
enough to survive in fossil form for billions of years, including seashells,
coral and some stromatolites -- rocks formed on this planet by ancient
microbial life along ancient shorelines, where sunlight and water were
plentiful.
The possibility of
stromatolite-like structures existing on Mars is why the concentration of
carbonates tracing Jezero's shoreline like a bathtub ring makes the area a
prime scientific hunting ground.
Mars 2020 is NASA's
next-generation mission with a focus on astrobiology, or the study of life
throughout the universe. Equipped with a new suite of scientific instruments,
it aims to build on the discoveries of NASA's Curiosity, which found that parts
of Mars could have supported microbial life billions of years ago. Mars 2020
will search for actual signs of past microbial life, taking rock core samples
that will be deposited in metal tubes on the Martian surface. Future missions
could return these samples to Earth for deeper study.
In addition to preserving
signs of ancient life, carbonates can teach us more about how Mars transitioned
from having liquid water and a thicker atmosphere to being the freezing desert
it is today. Carbonate minerals formed from interactions between carbon dioxide
and water, recording subtle changes in these interactions over time. In that
sense, they act as time capsules that scientists can study to learn when -- and
how -- the Red Planet began drying out.
Measuring 28 miles (45 kilometers)
wide, Jezero Crater was also once home to an ancient river delta. The
"arms" of this delta can be seen reaching across the crater floor in
images taken from space by satellite missions like NASA's Mars Reconnaissance
Orbiter. The orbiter's Compact Reconnaissance Imaging Spectrometer for Mars
instrument, or CRISM, helped produce colorful mineral maps of the "bathtub
ring" detailed in the new paper.
Scientists from NASA's Mars
2020 mission and the European Space Agency-Roscosmos ExoMars mission are in the
Australian Outback to hone research techniques before their missions launch to
the Red Planet in summer 2020. They are hoping to better understand how to
search for signs of ancient life on Mars. The Pilbara region of North West
Australia is home to "stromatolites," the oldest confirmed fossilized
lifeforms on Earth.
"CRISM spotted carbonates
here years ago, but we only recently noticed how concentrated they are right
where a lakeshore would be," said the paper's lead author, Briony Horgan
of Purdue University in West Lafayette, Indiana. "We're going to encounter
carbonate deposits in many locations throughout the mission, but the bathtub ring
will be one of the most exciting places to visit."
It isn't guaranteed that the
shoreline carbonates were formed in the lake; they could have been deposited
before the lake was present. But their identification makes the site's western
rim, called "the marginal carbonate-bearing region," one of the
richest troves of these minerals anywhere in the crater.
The Mars 2020 team expects to
explore both the crater floor and delta during the rover's two-year prime
mission. Horgan said the team hopes to reach the crater's rim and its
carbonates near the end of that period.
"The possibility that the
'marginal carbonates' formed in the lake environment was one of the most
exciting features that led us to our Jezero landing site. Carbonate chemistry
on an ancient lakeshore is a fantastic recipe for preserving records of ancient
life and climate," said Mars 2020 Deputy Project Scientist Ken Williford
of NASA's Jet Propulsion Laboratory in Pasadena, California. JPL leads the 2020
mission. "We're eager to get to the surface and discover how these
carbonates formed."
Jezero's former lake shoreline
isn't the only place scientists are excited to visit. A new study in Geophysical
Research Letters points to a rich deposit of hydrated silica on the edge
of the ancient river delta. Like carbonates, this mineral excels at preserving
signs of ancient life. If this location proves to be the bottom layer of the
delta, it will be an especially good place to look for buried microbial
fossils.
The Mars 2020 rover will
launch in July or August 2020 from Cape Canaveral, Florida. The Mars 2020
Project at JPL manages rover development for the Science Mission Directorate at
NASA Headquarters in Washington. NASA's Launch Services Program, based at the
agency's Kennedy Space Center in Florida, is responsible for launch management.
Mars 2020 is part of a larger
program that includes missions to the Moon as a way to prepare for human
exploration of the Red Planet. Charged with returning astronauts to the Moon by
2024, NASA will establish a sustained human presence on and around the Moon by
2028 through NASA's Artemis lunar exploration plans.
The Johns Hopkins University
Applied Physics Laboratory in Laurel, Maryland, leads MRO's CRISM
investigation.
For more information about
Mars 2020, go to:
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Journal References:
Briony H.N. Horgan, Ryan B.
Anderson, Gilles Dromart, Elena S. Amador, Melissa S. Rice. The mineral
diversity of Jezero crater: Evidence for possible lacustrine carbonates on Mars. Icarus,
2019; 113526 DOI: 10.1016/j.icarus.2019.113526
J.D. Tarnas, J.F. Mustard,
Honglei Lin, T.A. Goudge, E.S. Amador, M.S. Bramble, C.H. Kremer, X. Zhang, Y.
Itoh, M. Parente. Orbital identification of hydrated silica in Jezero
crater, Mars. Geophysical Research Letters, 2019; DOI: 10.1029/2019GL085584
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