- 4362 - OCEANS ON EXOPLANETS? - James Webb Space Telescope recently found traces of methane and carbon dioxide in the atmosphere of exoplanet “K2-18-b”, an exoplanet 8.6 times as massive as Earth about 120 light-years from us. The signature may be a sign of a water ocean.
------------------- 4362 - OCEANS ON EXOPLANETS?
- Searching for
liquid water on exoplanets is the key to finding life among the stars. If the atmosphere of an exoplanet has less
CO2 than its neighbors, there may be vast quantities of water on its surface,
or even life.
-
- Finding liquid
water on planets outside the solar system is a major challenge. Of the 5,000 or
so exoplanets we've discovered, liquid water hasn't been confirmed on any. The best scientists
can do is detect traces of water in exoplanet atmospheres and determine whether
planets could theoretically support water in the liquid state.
-
- We know that
initially, the Earth's atmosphere used to be mostly CO2, but then the carbon
dissolved into the ocean and made the planet able to support life for the last
four billion years.
-
- Once carbon is
dissolved in the oceans, tectonic activity then locks it away in Earth's crust,
creating an effective carbon sink. This is partly why our planet has
significantly lower CO2 levels compared with our neighbors. Earth's atmosphere is around 0.04% CO2,
whereas the atmospheres on Venus and Mars are both over 95% CO2.
-
- If scientists
observe a similarly low-carbon atmosphere on an exoplanet, it could indicate
the presence of vast oceans similar to our own. Looking for CO2 is easier than finding
liquid water. CO2 absorbs infrared radiation very well, it produces a strong signal that scientists
can detect.
-
- It's also possible
to perform this technique with existing telescopes, such as the James Webb
Space Telescope (JWST). Ground-based observations should also be possible
because of the specific wavelength CO2 is measured. Earth's atmosphere can absorb other
wavelengths.
-
- Another scenario
could contribute to an atmosphere low in carbon: life itself. The main ways
life on our planet captures carbon are through photosynthesis and making
shells, and around 20% of all carbon capture on Earth is caused by biological
processes.
-
- By leveraging the signature
of carbon dioxide, not only can we infer the presence of liquid water on a
faraway planet, but it also provides a path to identify life itself. JWST found the signature of water on
exoplanet WASP-96B.
-
- As researchers keep
discovering more exoplanets, more atmospheres will also be spotted. And this
technique could help figure out whether they could sustain life.
-
- The James Webb
Telescope also detected the coldest ice in the known universe. The latest observations of icy molecules will
help scientists understand how habitable planets form. The frozen molecules measured minus 440
degrees Fahrenheit.
-
- Molecular clouds,
made up of frozen molecules, gases and dust particles, serve as the birthplace
of stars and planets, including habitable planets. The JWST infrared camera investigated a molecular cloud called
“Chameleon I”, about 500 light-years from Earth.
-
- Within the dark,
cold cloud, the team identified frozen molecules like carbonyl sulfur, ammonia,
methane, methanol and more. These molecules will someday be a part of the hot
core of a growing star, and possibly part of future exoplanets. They also hold
the building blocks of habitable worlds: carbon, oxygen, hydrogen, nitrogen and
sulfur, a molecular cocktail known as “COHNS”.
-
- The initial, dark
chemistry stage are the formation of ice on the interstellar dust grains that
will grow into the centimeter-sized pebbles from which planets form. Stars and planets form within molecular
clouds like Chameleon I. Over millions of years, the gases, ices and dust
collapse into more massive structures.
-
- Some of these
structures heat up to become the cores of young stars. As the stars grow, they
sweep up more and more material and get hotter and hotter. Once a star forms,
the leftover gas and dust around it form a disk. This matter starts to collide, sticking
together and eventually forming larger bodies. One day, these clumps may become
planets. Even habitable ones like ours.
-
- The JWST sent back
its first images in July 2022, and scientists are currently using the $10
billion telescope's instruments to demonstrate what kinds of measurements are
possible. To identify molecules within Chameleon I, researchers used light from
stars lying beyond the molecular cloud. As the light shines towards us, it is
absorbed in characteristic ways by the dust and molecules inside the cloud.
These absorption patterns can then be compared to known patterns determined in
the lab.
-
- They found more
complex molecules they can't specifically identify. But the finding proves that
complex molecules do form in molecular clouds before they're used up by growing
stars. Identification of complex
organic molecules, like methanol and potentially ethanol, suggests that the
many star and planetary systems developing in this particular cloud will
inherit molecules in a fairly advanced chemical state.
-
- How a habitable
world like ours got its icy COHNS is still a major question among astronomers.
One theory is that COHNS were delivered to Earth via collisions with icy comets
and asteroids.
-
- The James Webb
Space Telescope also spotted six gigantic galaxies, each roughly the size of
our own Milky Way, that formed at a fast pace, taking shape just 500 million
years after the Big Bang. The six
massive galaxies, ages range between 500
to 800 million years after the Big Bang.
This group of galaxies are from the dawn of the universe and are so
massive they shouldn't exist.
-
- You just don't
expect the early universe to be able to organize itself that quickly. These
galaxies should not have had time to form.
Scientists don't know exactly when the first clumps of stars began to
merge into the beginnings of the galaxies we see today, but cosmologists
previously estimated that the process began slowly taking shape within the
first few hundred million years after the Big Bang.
-
- Currently theories
suggest that 1 to 2 billion years into the universe's life, these early
proto-galaxies reached adolescence, forming into dwarf galaxies that began
devouring each other to grow into ones like our own.
-
- Because light
travels at a fixed speed through the vacuum of space, the deeper we look into
the universe, the more remote light we intercept and the further back in time
we see. By using the James Webb Space Telescope to peer roughly 13.5 billion
years into the past, the astronomers found that enormous galaxies had already
burst into life very quickly after the Big Bang, when the universe was just 3%
of its current age.
-
- The galaxies are
so massive, they are in tension with 99 percent of the models for
cosmology. This means that either the
models need to be altered, or scientific understanding of galaxy formation
requires a fundamental rethink.
-
- The Milky Way forms
about one to two new stars every year.
Some of these galaxies would have to be forming hundreds of new stars a
year for the entire history of the universe.
The amount of mass we discovered means that the known mass in stars at
this period of our universe is up to 100 times greater than we had previously
thought.
-
- Previous imaging
of the early universe by the Hubble Space Telescope didn't detect the giant
galaxies, but JWST is about 100 times more powerful than Hubble. The
$10 billion JWST launched to a gravitational stable location beyond the
moon's orbit known as a “Lagrange point”, in December 2021.
-
- The space
observatory was designed to read the earliest chapters of the universe's
history in its faintest glimmers of light which have been stretched to infrared
frequencies from billions of years of travel across the expanding fabric of
space-time.
-
- The next step will
be to take a spectrum image of the giant galaxies providing accurate distances and a better idea of the
chemical makeup of the monsters hiding at the beginning of the universe.
-
-
February 22, 2024
OCEANS ON
EXOPLANETS? 4362
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