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[deleted] t1_jdwc1sj wrote

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gg_account t1_jdx6fuh wrote

They modeled several scenarios and this temperature almost exactly matches an airless black rock.

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mmomtchev t1_jdwcxmn wrote

No one said that all planets must have an atmosphere. I agree that temperature by itself is not a reason for the absence of the atmosphere - however close proximity to the star is - since the stellar wind will strip it, unless the planet has a very strong magnetic field. Venus is not that close to the star - its normal temperature without the green house effect wouldn't have been so high. Also, when you measure the temperature of a planet this way - it is not the the temperature of the surface - but of the emitting layer. And if the emitting layer is so hot - it is probably the ground and there is probably no atmosphere.

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lezboyd t1_jdwu0j2 wrote

Plus, Venus is technically in the Sun's Goldilocks Zone. If it weren't for the runaway greenhouse effect, it might as well have been habitable. There are some models that do hint that Venus had water oceans like Earth for a few million years before its atmosphere took a turn.

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Just_wanna_talk t1_jdz0trg wrote

What was venus' atmosphere like before? Do we know?

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lezboyd t1_jdz42z2 wrote

If you're curious not just about Venus, but for most of the planets and how they evolved, then I'd recommend watching the Mini Series 'The Planets (2019)' hosted by Brian Cox. It's only 5 episodes and they're pretty informative.

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StrangeTangerine1525 t1_jdwzw75 wrote

Yes but planets can lose gas to space via thermal escape, at very high rates depending on the temperature. There is also photochemical reactions caused by UV rays that can also drive atmospheric escape, so this planet could have a strong magnetic field and still have no atmosphere, especially if it is this close to its host star, a relatively active red dwarf at that.

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PhoenixReborn t1_je2sv0w wrote

>Astronomers think that's too high for the planet to have an atmosphere." Err, Venus?

It's not that a high temperature prevents an atmosphere. The high temperature on the day side is evidence against an atmosphere. A dense atmosphere would redistribute heat around the planet, resulting in a cooler day side. That's not what was observed.

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