After initially detecting tremors assumed to be
generated by the cooling of Mars' innards and volcanic activity, NASA's InSight
Martian lander has now discovered meteorite strikes. Despite the small size of
the space rocks that have been dropping nearby, InSight is so sensitive that it
has been able to detect seismic waves from collisions up to 290 kilometres (180
miles) away. Now, NASA has released the sound of meteorites striking Mars.
The atmosphere of the Earth is routinely bombarded
by particles as small as sand grains and as large as enormous rocks. These can
create breathtaking sky displays, but only the larger ones actually touch the
earth as opposed to bursting into flames as they descend. On Mars, the
atmosphere is significantly thinner, allowing for far greater object passage.
But being aware of this and actually perceiving it are two different things.
Despite years of Martian rovers and landers, none of them had ever experienced
the seismic waves brought on by an incoming space rock.
Although InSight has been on Mars since 2018, it
wasn't until an incident on September 5, 2021 that scientists first saw seismic
waves from an impact, as is now documented in a recent publication. But the
wait was worthwhile. The meteoroid exploded due to considerable friction that
was produced even by the weak Martian atmosphere. Not just one, but three
darkish marks left behind by the object after it disintegrated were spotted by
NASA's Mars Reconnaissance Orbiter.
Dr. Ingrid Daubar of Brown University said in a
statement, "It was quite exciting." "The pictures of the actual
craters are my favourites. Those impact craters became stunning after three
years of waiting."
Daubar and co-authors explored further after
determining InSight is capable of detecting the seismic waves from meteorite
impacts. Re-analyzing InSight's historical data, they discovered three less
significant occurrences from 2020 and early 2021. Each produced seismic waves
that were less than a Marsquake of magnitude 2.0.
In three instances, InSight also detected the
object's auditory wave as it passed through the atmosphere. One detection was,
perhaps by coincidence, only five days away from the impact that initially drew
their notice.
Planetary scientists are interested in the craters
for reasons other than aesthetics. All other mission-related data is calibrated
by knowing the exact position of the source of the impacts, according to
Daubar.
The location
and magnitude of the consequences are "validated by this," according
to our estimations. Additionally, it will make it possible for researchers
using InSight's data to more precisely detect upcoming collisions.
Daubar and his associates were perplexed that
striking space objects hadn't been discovered earlier. Mars should meet more
asteroids due to its proximity to the asteroid belt compared to Earth, which accounts
for its smaller size. Although the Red Planet is less seismically active than
our own, InSight has already recorded 1,300 Marsquakes, which previous Mars
landers may not have been sensitive enough to record.
The authors speculate that InSight may have actually
detected seismic waves from previous meteorite impacts, but that these may have
been incorrectly interpreted because the crew wasn't aware of the waves'
particular structure. Now that there are four confirmed incidents, they are
hoping to discover more.
The age of the Martian landscape may be determined
by measuring the frequency of crater-forming events, which enables us to
determine how long craters like this last before being covered by sand or other
processes. Dr. Raphael Garcia, the study's principal author from France's
Institut Supérieur de l'Aéronautique et de l'Espace, explained that impacts
serve as the solar system's clocks.
Ironically, the InSight/Reconnaissance Orbiter
partnership outperforms all of our numerous Earth-based seismic satellites and
equipment. The seismic and infrasound detections from the meteorite's passage
through the atmosphere have only been matched to one crater on Earth. Numerous
hits have been detected by the seismic network set up by the Apollo astronauts,
but none of them have been linked to recently produced craters.
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