XPost: alt.astronomy, alt.fan.heinlein
And this is why I personally would not be at all surprised if
future exploration discovers life on Mars with genetic connections
to life on Earth. "panspermia"
from
https://www.space.com/mars-meteorites-5-craters-tharsis-elysium
200 meteorites on Earth traced to 5 craters on Mars
News
By Victoria Corless published August 23, 2024
Astronomers have traced the origins of 200 meteorites to five impact
craters in two volcanic regions on Mars, known as Tharsis and Elysium.
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craggy grey rocks float above a reddish orange planet
Illustration of a large meteorite above Mars. (Image credit:
Pitris/Getty Images)
Believe it or not, debris from Mars has frequently made its way to Earth
after powerful impacts hit the Red Planet's surface and launch it into
space.
There have been at least 10 of these meteorite-forming events in Mars'
recent history. When these massive impacts occur, meteorites can be
flung away from the Red Planet with enough velocity that they break free
of Mars' gravitational pull to enter orbit around the sun, with some
eventually falling to Earth.
Scientists at the University of Alberta have now traced the origins of
200 of these meteorites to five impact craters in two volcanic regions
on Mars, known as Tharsis and Elysium. "Now, we can group these
meteorites by their shared history and then their location on the
surface prior to coming to Earth," said Chris Herd, curator of the
university's meteorite collection and professor in the faculty of
science, in a statement.
Meteorites fall to Earth all the time — an estimated 48.5 tons (44,000 kilograms) of meteorite material falls each day, according to NASA —
though the majority make it to the surface as tiny unnoticeable
particles of dust. Determining their origins can often be difficult, but
in the 1980s, scientists became suspicious of a group of meteorites that appeared to have volcanic origins with ages of 1.3 billion years.
This meant that these rocks had to have come from a celestial body with
recent (in geological terms) volcanic activity, making Mars a likely
candidate. However, proof came when NASA's Viking landers were able to
compare the composition of Mars' atmosphere with trapped gases found in
these rocks.
Identifying exactly from where on Mars they originated was previously
difficult to do. The team noted in their paper that this difficulty
arose from using a technique called spectral matching, a technique used
to identify and compare the composition of materials by analyzing the
patterns of light they absorb or emit.
However, this method is limited by factors such as terrain variability
and extensive dust cover, which can skew spectral signals, especially on younger terrains like Tharsis and Elysium. But knowing exactly where
these Martian meteorites came from would allow scientists to better
piece together the planet's geological past.
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"[It would] enable the recalibration of Mars' chronology, with
implications for the timing, duration and nature of a wide range of
major events through Martian history," said Herd. "I call that the
missing link — to be able to say, for example, the conditions under
which this meteorite was ejected were met by an impact event that
produced craters between 10 and 30 kilometres across."
a dark grey pockmarked rock
A Martian meteorite known as Amgala 001, found in Western Sahara in
2022. (Image credit: Wikimedia Commons/Steve Jurvetson)
The team combined high-resolution simulations of impacts into a
Mars-like planet. "One of the major advances here is being able to model
the ejection process, and from that process be able to determine the
crater size or range of crater sizes that ultimately could have ejected
that particular group of meteorites, or even that one particular
meteorite," said Herd.
The model's output allowed the team to determine the impact events'
"peak shock pressures" and the duration the rocks were exposed to these pressures. This can be determined from "shock features" observed in the meteorites—for example, unique mineral changes, impact glass, and
special fracture patterns.
From this data, Herd and his colleagues were able to estimate the size
of the impact craters that could have launched the meteorites, as well
as how deep the rocks were buried before the impact. Although these
depth estimates come with some uncertainty, the researchers compared
them with the local geology of possible source craters and the
characteristics and ages of the meteorites to see if they align.
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"[Our modelling approach] allows us to say, of all these potential
craters, we can narrow them down to 15, and then from the 15 we can
narrow them down even further based on specific meteorite
characteristics," he said. "We can maybe even reconstruct the volcanic stratigraphy [the geological record], the position of all these rocks,
before they got blasted off the surface."
This could help the scientists better understand when volcanic events on
Mars occurred, the different sources of Martian magma, and how quickly
craters formed during an era of low meteorite bombardment on the Red
Planet known as the Amazonian period, some 3 billion years ago.
"It is really amazing if you think about it," Herd added. "It's the
closest thing we can have to actually going to Mars and picking up a rock."
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Victoria Corless
Victoria Corless
Contributing Writer
A chemist turned science writer, Victoria Corless completed her Ph.D. in organic synthesis at the University of Toronto and, ever the cliché,
realized lab work was not something she wanted to do for the rest of her
days. After dabbling in science writing and a brief stint as a medical
writer, Victoria joined Wiley’s Advanced Science News where she works as
an editor and writer. On the side, she freelances for various outlets, including Research2Reality and Chemistry World.
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