Can Mercury is a hot jupiter before?

[AlexChan]

I do not know too much about astrophysics,
but is it possibility of this?

[selden]

It seems unlikely to me.

The best known "hot jupiter" where the atmosphere is seen is in a system that's probably about the same age as our own. It's much closer to its sun than Mercury is, but its atmosphere already has lasted for about as long as Mercury has existed. Since it's hotter than Mercury is, it is losing its atmosphere faster than a planet at Mercury's position would. Although the rate of loss seems large to us, the fraction lost per year is a very, very tiny fraction of the planet's total atmosphere.

See http://vo.obspm.fr/exoplanetes/encyclo/ ... 09458&p2=b
and
http://www.space.com/scienceastronomy/s ... 30312.html

[PlutonianEmpire]

I think he was asking if there was a possibility that mercury may have once been a hot jupiter...

[selden]

And my answer was "probably not".

A hot jupiter would still exist, not be stripped to a metallic core.

Also, Mercury is heavily cratered. That kind of cratering happened early in the formation of the solar system. The remaining core of a gas giant would have few, if any, craters, since it would have been protected by a dense atmosphere.

[ajtribick]

Mercury's rather further from the Sun than a hot Jupiter would be: in fact the extrasolar Neptune-mass planet HD 69830 c receives a similar amount of radiation from its star as Mercury does from the Sun, and is predicted to have experienced negligible mass loss over its history.