- 4313 - 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.
------------------------- 4313 - OCEANS ON EXOPLANETS
- Searching for
liquid water on exoplanets is the key to finding life among the stars, and now,
scientists have proposed a new strategy that might improve the chances of finding it.
-
- Researchers have
hypothesized that 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.
-
- Currently, finding
liquid water on planets outside the solar system is a major challenge. Of the
over 5,000 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 or so.
-
- 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, meaning 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 stop experiments at
other wavelengths by partially absorbing the signals.
-
- 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 these
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.
-
- Although the
approach looks like it'll work in principle, there may still be hurdles, as
it's not clear how many terrestrial exoplanets also have atmospheres. As researchers keep discovering more
exoplanets, more atmospheres will also be spotted. And this technique could
help figure out whether they could sustain life.
-
-
January 12, 2023
OCEANS ON
EXOPLANETS 4313
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