Like the USS Enterprise, the James Webb Space Telescope reveal secrets about new worlds.
New observations by the world-renowned telescope has revealed a planet covered in a deep boiling water ocean – also known as a hycean world.
The water world, TOI-270 d, is a sub-Neptune distant exoplanet that resides around 70 light years away.
The observations of the planet revealed water vapour and chemical signatures of methane and carbon dioxide in the atmosphere – a chemical mix which is consistent with what would be expected from a water world and a hydrogen-rich atmosphere.
Researchers from the University of Cambridge say that although the planet may have a surface that is covered with an ocean, they do not envisage a seascape.
‘The ocean could be upwards of 100 degrees or more’, said Professor Nikku Madhusudhan, who led the analysis.
The team says that an ocean this hot could still be liquid if the atmospheric pressure was high enough, ‘but it’s not clear if it would be habitable’.
This reasoning has been debated by a Canadian team that detected the same atmospheric chemicals but thinks the planet would be too hot for liquid water and instead would have a rocky surface with a dense atmosphere of hydrogen and water vapour.
However, the possible water world does not have ammonia, which should occur naturally in a hydrogen-rich atmosphere but would show lower rates if there was an ocean below – as ammonia is soluble.
It’s also tidally locked, meaning that one side of it always faces its host star, and the other is always in darkness which will create an extreme temperature contrast.
‘The ocean would be extremely hot on the day side. The night side could potentially host habitable conditions,’ said Professor Madhusudhan.
The planet is also thought to have a crushing atmosphere that is at tens or hundreds of times the pressure at the Earth’s surface, as steam rolls off the ocean.
Its oceans would run tens to hundreds of kilometres deep, with a high-pressure ice seabed, and beneath that a rocky core.
TOI-270 d: the lowdown
- It is a Neptune like exoplanet (a planet not in our solar system) orbiting an M-type star
- Its mass is 4.78 Earths
- It takes around 11.4 days to complete one orbit of its star
- It was discovered in 2019
Professor Björn Benneke, of the University of Montreal, carried out additional observations of the planet and thinks the planet is too hot for liquid water.
‘The temperature in our view is too warm for water to be liquid,’ he said.
Professor Benneke said the atmosphere appeared to contain a significant amount of water vapour – too much for the existence of an ocean to be plausible.
‘It’s almost like a thick, hot fluid,’ he said.
Another chemical compound, carbon disulphide, was detected and is linked to biology on Earth.
‘We can’t tie [carbon disulphide] to biological activity,’ said Professor Madhusudhan.
‘In a hydrogen-rich atmosphere, it is relatively easy to make it. But if we’re able to measure the unique molecule it’s promising that we should be able to measure habitable planets in the future.
‘We need to be extremely careful about how we communicate findings on this kind of object. It’s easy for the public to jump on to the idea that we’re finding life already.’
The study is published in the journal Astronomy and Astrophysics Letters.
Get in touch with our news team by emailing us at webnews@metro.co.uk.
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