Could this be a new Earth? NASA studies an exoplanet that may have water and an atmosphere

Every now and then science gives us a glimmer that our “place in the cosmos” might not be as unique as once thought – somewhere a few people may be dreaming about right now – and this is one of those moments.

A planet in the “Goldilocks zone”

TRAPPIST-1 e – remember we spoke about that before – is one of seven Earth-sized planets orbiting a cool red dwarf star about 40 light years away. What makes it special is that it lies at just the right distance – neither too close nor too far from its star – for liquid water to theoretically exist on its surface. NASA’s James Webb Space Telescope (Webb), using its Near-Infrared Spectrograph (NIRSpec), has made multiple observations of the planet during transits (when it passes in front of its star).

What do the observations tell us so far?

Here’s a breakdown of what’s been revealed in various reports:

• Primary atmosphere ruled out

Early Webb data show that TRAPPIST-1 e almost certainly does not have a hydrogen-helium rich “primary” atmosphere – the kind a planet might start with shortly after formation. Stellar flares and strong radiation from its parent star likely stripped that off.

• Secondary atmosphere possible

Instead of being bare, the planet may have built up a “secondary” atmosphere composed of heavier gases similar to what Earth has e.g. nitrogen, carbon dioxide, etc. Such an atmosphere would be more resistant to being blown away.

• Liquid water might be possible

If a secondary atmosphere exists and includes greenhouse gases like CO2, it could trap enough heat to keep surface water liquid – either globally, or at least on the side of the planet permanently facing its star. Other areas might be icy if tidally locked.

• What we don’t know yet

Researchers haven’t detected exactly what gases are in any atmosphere, or even confirmed that the atmosphere is there. There’s also uncertainty about how much water (if any) is present, and how extreme the temperature differences would be between parts of the planet.

Is TRAPPIST-1 e habitable?

Sorry to disappoint, but even with water and atmosphere in play, habitability isn’t guaranteed. Here are some of the limiting factors:

The star, TRAPPIST-1, is very active. Frequent flares can bombard planets with radiation, stripping atmospheres or breaking apart molecules.

If the planet is tidally locked (always showing the same face toward the star), the “day side” could be scorchingly hot while the “night side” is freezing, unless atmospheric or ocean circulation redistributes heat.

The amount of greenhouse gas matters. Too little and it’s frozen; too much and it’s like Venus. Lessons from Earth, Mars, and Venus show how narrow that window can be.

Is TRAPPIST-1 e a “new Earth”? The verdict

TRAPPIST-1 e stands out as one of the best candidates we have for a planet that could be Earth-like in important ways. It’s in the habitable zone, it might have shed its original light atmosphere and built a heavier one, and liquid water might be possible.

So clearly we’re not there yet, but the next rounds of Webb observations may potentially tip the scales.

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