How did Earth-like Venus turn inhospitable? NASA's James Webb Space Telescope could help decipher secret

A newly discovered exoplanet called LP 890-9c, located 98 light-years away from Earth, could provide insights into how habitable planets like Earth can transform into inhospitable worlds like Venus.

The exoplanet orbits a small and cool red dwarf star, and its position near the inner edge of the star's habitable zone makes it an intriguing candidate for study.

SPECULOOS-2c: Venus-like or Earth-like exoplanet

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The exoplanet LP 890-9c or SPECULOOS-2c was discovered back in September 2022. As per Space.com, the planet has a diameter greater than Earth by about 40 per cent. Just like our planet orbits the Sun, this small and cool planet also orbits its star — every 8.5 Earth days at a distance of 1.7 million miles or 2.8 million kilometres.

"LP 890-9 c lies very close to the inner edge of the conservative habitable zone (HZ)". However, despite the exoplanet's proximity to its star, the planet is cool. In comparison, Earth is 152.07 million kilometres away from the sun.

This as per researchers, means that even close to a star, a planet's temperatures can be mild.

LP 890-9c, Venus and habitable planets

Using the exoplanet as a model, a research team led by Lisa Kaltenegger from the Carl Sagan Institute at Cornell University has modelled the possible climatic and atmospheric states of LP 890-9c and explored how the James Webb Space Telescope (JWST) could distinguish between them.

LP 890-9c's location in its planetary system is similar to Venus' position in our solar system, with both planets positioned at the inner edge of the habitable zone.

While Venus became an inhospitable world due to a runaway greenhouse effect, not all planets in similar positions will necessarily follow the same path.

Venus lacks a magnetic field, which allowed the solar wind to strip away its water molecules. However, if LP 890-9c possesses a strong magnetic field, it may be able to retain water vapour in its atmosphere and maintain habitability.

"Looking at this planet will tell us what's happening on the inner edge of the habitable zone — how long a rocky planet can maintain habitability when it starts to get hot," said Kaltenegger in a statement.

The team developed models of LP 890-9c based on measured parameters such as mass and radius. The models also considered factors such as chemical composition, surface temperature, atmospheric pressure, cloud cover, and more.

Five different models were created, ranging from an Earth-like planet but hotter, to varying degrees of atmospheric water vapour and greenhouse effects, culminating in a model resembling Venus.

"This planet is the first target where we can test these different scenarios," said Kaltenegger.

"If it's still a hotter Earth — hot, but with liquid water and conditions for life — then the inner edge of the habitable zone (around all stars) could be teeming with life," speculated the researcher.

James Webb Telescope and the search for habitable planets

Another study led by Jonathan Gomez Barrientos from the California Institute of Technology suggests that the JWST could observe LP 890-9c for a few transits across its host star to determine the planet's atmospheric composition.

This could provide insights into whether the planet has a steamy, water-rich atmosphere similar to Earth, or if it is more akin to Venus.

The observations and analysis of LP 890-9c could shed light on the inner edge of habitable zones around stars and the longevity of rocky planets in such regions. Even if LP 890-9c proves too hot for life, studying its evolution and fate can provide valuable information about Earth's own future as our sun continues to evolve and grow brighter.

As per Kaltenegger, "It will teach us something fundamental about how rocky planets evolve with increasing starlight and about what will one day happen to us and Earth."

The research findings were published in two papers in the Monthly Notices of the Royal Astronomical Society.