Alien Microbe Life on Numerous Super Earth Exoplanets Should Be Observed By 2025

Ocean covered exoplanets that are up to 2.6 times bigger than Earth should have microbial life which the James Webb Space Telescope should detect. The James Webb should launch this year. Planets of this size dominate the known exoplanet population, although they have not been studied in nearly as much detail as super-Earths. Hycean worlds are likely quite common, meaning that the most promising places to look for life elsewhere in the Galaxy may have been hiding in plain sight.

The Cambridge team identified a sizeable sample of potential Hycean worlds which are prime candidates for detailed study with next-generation telescopes, such as the James Webb Space Telescope (JWST), which is due to be launched later this year. These planets all orbit red dwarf stars between 35-150 light years away: close by astronomical standards. Already planned JWST observations of the most promising candidate, K2-18b, could lead to the detection of one or more biosignature molecules.

The Astrophysical Journal – Habitability and Biosignatures of Hycean Worlds

However, size alone is not enough to confirm whether a planet is Hycean: other aspects such as mass, temperature and atmospheric properties are required for confirmation.

When trying to determine what the conditions are like on a planet many light years away, astronomers first need to determine whether the planet lies in the habitable zone of its star, and then look for molecular signatures to infer the planet’s atmospheric and internal structure, which govern the surface conditions, presence of oceans and potential for life.

Astronomers also look for certain biosignatures which could indicate the possibility of life. Most often, these are oxygen, ozone, methane and nitrous oxide, which are all present on Earth. There are also a number of other biomarkers, such as methyl chloride and dimethyl sulphide, that are less abundant on Earth but can be promising indicators of life on planets with hydrogen-rich atmospheres where oxygen or ozone may not be as abundant.

Cambridge researchers have identified a new class of habitable planets, dubbed ‘Hycean’ planets – ocean-covered planets with hydrogen-rich atmospheres – which are more numerous and observable than Earth-like planets.

The researchers say the results, reported in The Astrophysical Journal, could mean that finding biosignatures of life outside our Solar System within the next few years is a real possibility.

“Hycean planets open a whole new avenue in our search for life elsewhere,” said Dr Nikku Madhusudhan from Cambridge’s Institute of Astronomy, who led the research.

Many of the prime Hycean candidates identified by the researchers are bigger and hotter than Earth, but still have the characteristics to host large oceans that could support microbial life similar to that found in some of Earth’s most extreme aquatic environments.

These planets also allow for a far wider habitable zone, or ‘Goldilocks zone’, compared to Earth-like planets. This means that they could still support life even though they lie outside the range where a planet similar to Earth would need to be in order to be habitable.

Thousands of planets outside our Solar System have been discovered since the first exoplanet was identified nearly 30 years ago. The vast majority are planets between the sizes of Earth and Neptune and are often referred to as ‘super-Earths’ or ‘mini-Neptunes’: they can be predominantly rocky or ice giants with hydrogen-rich atmospheres, or something in between.

Most mini-Neptunes are over 1.6 times the size of Earth: smaller than Neptune but too big to have rocky interiors like Earth. Earlier studies of such planets have found that the pressure and temperature beneath their hydrogen-rich atmospheres would be too high to support life.

However, a recent study on the mini-Neptune K2-18b by Madhusudhan’s team found that in certain conditions these planets could support life. The result led to a detailed investigation into the full range of planetary and stellar properties for which these conditions are possible, which known exoplanets may satisfy those conditions, and whether their biosignatures may be observable.

The investigation led the researchers to identify a new class of planets, Hycean planets, with massive planet-wide oceans beneath hydrogen-rich atmospheres. Hycean planets can be up to 2.6 times larger than Earth and have atmospheric temperatures up to nearly 200 degrees Celsius, depending on their host stars, but their oceanic conditions could be similar to those conducive for microbial life in Earth’s oceans. Such planets also include tidally locked ‘dark’ Hycean worlds that may have habitable conditions only on their permanent night sides, and ‘cold’ Hycean worlds that receive little radiation from their stars.

We investigate a new class of habitable planets composed of water-rich interiors with massive oceans underlying H2-rich atmospheres, referred to here as Hycean worlds. With densities between those of rocky super-Earths and more extended mini-Neptunes, Hycean planets can be optimal candidates in the search for exoplanetary habitability and may be abundant in the exoplanet population. We investigate the bulk properties (masses, radii, and temperatures), potential for habitability, and observable biosignatures of Hycean planets. We show that Hycean planets can be significantly larger compared to previous considerations for habitable planets, with radii as large as 2.6 R⊕ (2.3 R⊕) for a mass of 10 M⊕ (5 M⊕). We construct the Hycean habitable zone (HZ), considering stellar hosts from late M to Sun-like stars, and find it to be significantly wider than the terrestrial-like HZ. While the inner boundary of the Hycean HZ corresponds to equilibrium temperatures as high as ∼500 K for late M dwarfs, the outer boundary is unrestricted to arbitrarily large orbital separations. Our investigations include tidally locked “Dark Hycean” worlds that permit habitable conditions only on their permanent nightsides and “Cold Hycean” worlds that see negligible irradiation. Finally, we investigate the observability of possible biosignatures in Hycean atmospheres. We find that a number of trace terrestrial biomarkers that may be expected to be present in Hycean atmospheres would be readily detectable using modest observing time with the James Webb Space Telescope (JWST). We identify a sizable sample of nearby potential Hycean planets that can be ideal targets for such observations in search of exoplanetary biosignatures.

SOURCES-Astrophysical Journal, Cambridge University
Written by Brian Wang,

19 thoughts on “Alien Microbe Life on Numerous Super Earth Exoplanets Should Be Observed By 2025”

  1. With current telescopes if we detect a transiting exoplanet we get the radius of the planet from the dip in light from the star. Then we also look at the radial velocity variations to get the mass of the planet. Of course there will be error bars on both those figures.
    Given the mass & radius we get the density & so get limits on what it can be made of.

  2. Didn't notice if any reasonable candidates had been identified within our neighborhood Local Bubble of the inner rim of our home-sweet-home Orion-Cygnus Arm of the MW.

    From the article

    These planets all orbit red dwarf stars between 35-150 light years away:

  3. 'rare' is relative . Even one-in-a-billion stars is low-thousands of possibilities just in Milky Way.

  4. It’s a shame that there are likely many planets with life throughout the Milky Way, but they are just too far away.

  5. My hope is that one day we'll have an array of telescopes spread throughout the solar system, which work in unison.

  6. always wanted to know the business case for making a one-man 'popular sciences' blog. Probably a delicate balance between attracting and maintaining a specific 'techno-literate' audience without getting too esoteric (reduces audience and creates impermeable and off-putting jargon land) while keeping current and widely-appealing articles. Likely only possible if one is passionate/obsessive about a few industries and their key players with a flexible day-job schedule. As the audience and its expectations grow, I assume almost daily posts, highly interactive comments, and maintenance becomes expensive and time-consuming; often leading to very cut-paste content, difficult fact-checking/ grammar/context comprehension, and a tendency to sprinkle profusely with hyper-controversy and popular links. I certainly couldn't/ wouldn't do it.

  7. Are we sure on the 10x Earth Mass for such a mini-neptune? I am picturing a huge freezie-ball with many-many 100s mi deep ocean liquids/ slushes/ ices and an insignificant metallic/rocky core — and a not-even thick/hazy, almost soupy/sludgy atmosphere. Are we launching off this place or a floating platform practically at LEO, if such a concept makes sense…

  8. You'd never be able to leave such a planet with chemical propulsion; Earth is right at the limit for that. It would be nuclear or nothing, even for putting satellites into low orbit.

  9. Just as a general note concerning writing: You should have led with a definition of "hycean", instead of repeatedly using it as though everybody would know what it meant, and then tossing a definition in halfway through the post.

    You really, desperately need a proof reader/editor.

  10. Gravity is easy. Using the figure of 2.6 x the radius & 10 x the mass of earth, I get just under 1.5 x the gravity.
    Everything else is going to have a much broader range of possibilities

  11. not convinced on life though… even the most exotic extremophiles (barely definable as life) would have a hard time on these predicted bodies… evolving complexity, after that? Maybe under the panspermia hypothesis…

  12. Fair. Further articles discuss 'Dark' Hycean planets with amazing day-night energy distributions that could allow smaller areas of habitability on planets, even moons, otherwise uninhabitable, such as with dark sides (tidally locked), small areas at poles, bizarrely-elliptical solar system orbits, multi-year/decade seasons…

  13. Ah but only a quarter-billion years ago – a different time. Though perhaps we will have a new Panthalassa over the next few millenia.
    Ho-hum – was kind of hoping for a Kamino or Monean Water World as TV promised.

  14. Let's notice "Hycean" are most likely "Venusian" worlds or rather mini-Neptunes.

    Pressure-cooker worlds with thick atmospheres and rampant greenhouse effects taking the temperatures way above the range of complex organic chemistry.

    Nevertheless, these worlds could hit the right balance of temperature farther from their stars Goldilocks zone, allowing panthalassa worlds with a thick atmosphere to exist somewhere.

    I assume those are the ones they are excited about.

  15. Reduced chances due to us being on the unfashionable spur of an out-of-the-way backwater Carina-Sagitarius Arm, far and distant from even the uptown section of the Galactic Center – though I heard it was a lot more 'extinction-y' closer in.

  16. Hycean? — Hard for me to parse what gravity would be like at the surface, water pressure at 1 atmosphere, what kind of underwater structures could exist, and how the troposphere and stratosphere layers would work compositionally. Fascinating. Didn't notice if any reasonable candidates had been identified within our neighborhood Local Bubble of the inner rim of our home-sweet-home Orion-Cygnus Arm of the MW. See BeSSel project for more 'local' travelling info (galactic morphological classification project).

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