- 4376 - WHY STUDY COMETS? Comets can teach us about finding life beyond Earth? The importance of studying impact craters, planetary surfaces, exoplanets, astrobiology, and solar physics, and this myriad of scientific disciplines teach scientists and the public regarding the search for life beyond Earth.
------------------- 4376 - WHY STUDY COMETS?
- For star gazers,
comets are some of the most attention-grabbing objects in the sky. They move,
they change their shape, appearance, and their brightness, as they travel
through their orbits. Yet they are scientifically important for other reasons.
When they venture towards the Sun (approach their orbital perihelion), they
show what they are made of, by emitting gas and dust from the comet nucleus.
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- They are the most
accessible, least altered solar system bodies, and they are accessible because
they come close to the Sun and Earth. They have retained a significant portion
of their volatiles over time, and they have likely played a significant role in
transporting volatile material through the solar system.
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- While comets have
been explored via spacecraft for only the last few decades, their observational
history dates back several thousand years, including Halley’s Comet, which
becomes visible from Earth every 75-79 years, and was most famously illustrated
on the Bayeux Tapestry in the 11th century that depicted the Norman invasion of
England in 1066, known as the Battle of Hastings.
-
- Like most
astronomical phenomena throughout history, the comet observations were
initially perceived as either positive or negative omens, whether it be for
fortune or health. It was the legendary
Greek philosopher, Aristotle, who proclaimed during the 4th century BCE that
comets were atmospheric phenomena. This belief went unopposed until a series of
physicists and mathematicians made their own scientific assertions about
comets, including the French mathematician, Jean Pena, who deduced that comets were
of celestial origin as opposed to terrestrial origin.
-
- This was later
confirmed by Tycho Brahe, who used the Great Comet of 1577 to measure its
parallax and deduced that comets are of astronomical nature, as well. Since the
dawn of the Space Age, several spacecraft missions have visited comets
up-close, including Halley’s Comet on a few occasions, offering scientists
incredible opportunities to learn more about these mysterious balls of ice.
-
- Comets change
throughout their orbits, as well as their behavior in different orbital passes
near the sun (perihelion passages). Each variance provides more information as
to the cause and nature of its behavior. It also makes the behavior difficult
to interpret.
-
- Comets are massive
planetary bodies comprised of ice and dust that orbit the Sun in the Oort Cloud
and are remnants of the formation of the solar system, making them
approximately 4.6 billion years old.
-
- While comets put
on fantastic displays when they travel close to the Sun, they originate in the
far reaches of the solar system known as the Kuiper Belt, which is home to the
dwarf planet, Pluto. As their orbits take them closer to the Sun, the
increasing heat causes the volatiles within the comet’s core, known as its
nucleus, to burn off and evaporate into the cosmos, producing the spectacular
tails we see from Earth.
-
- Several decades
ago, the paradigm for comet activity was that water sublimation drove the
activity in most cases, as the comet came within distances near 3 or 4
Astronomical Units to the Sun. Over the last decade these observatories showed
CO [carbon monoxide] and CO2 [carbon dioxide] driven activity, or at least that
these species were responsible for a significant portion of the outgassing for
comets.
-
- Comets have been
hypothesized to have brought the necessary ingredients to Earth for life to
emerge in a process called panspermia, and some scientists even postulated
using comets to disperse the ingredients for life throughout the Milky Way
Galaxy.
-
- Regarding the
ingredients, the European Space Agency’s Rosetta spacecraft discovered in 2020
that comet “67P/Churyumov–Gerasimenko” contained phosphorus, which is one of
the most crucial ingredients for life to emerge. But if comets brought life to
Earth, could this be the same for other worlds throughout the cosmos? All
things considered, what can comets teach us about finding life beyond Earth?
-
- Observations show
us that comets carry the chemical building blocks of life, and those chemical
species can also be found in exo-solar systems; they are ubiquitous. Many
classes of organic compounds have been detected in comets, compounds that are
also found in spectra of exo-systems.
-
- Our currently
single example of an exo-comet, “2I/Borisov”, looked like a fairly typical Oort
cloud comet, and so we might expect that primordial chemistry might be similar
in exo-systems.
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-
March 3, 2024 WHY
STUDY COMETS? 4376
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Monday, March 4, 2024
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