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gunnervi t1_iu24xk1 wrote

Reply to comment by SolarParasite in Magma on Mars Likely - Until now, Mars has been generally considered a geologically dead planet. An international team of researchers led by ETH Zurich now reports that seismic signals indicate volcanism still plays an active role in shaping the Martian surface. by GeoGeoGeoGeo

The average density of mars is about 70% that of earth. so we'd expect that its made of relatively less metal than earth and more light elements like carbon, oxygen, and silicon. (this is complicated somewhat by compression, but you can do some complicated modelling which suggests that Mars is indeed a slightly different composition than the Earth (its more similar to the Moon)

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PleasantlyUnbothered t1_iu2iqxu wrote

Are the planets largely less dense as you get further away? Like the elements were light enough to make it further out in larger quantities? Considering it’s rocky planets, then gas planets, it seems that way. I’m sure there’s a huge margin of error when taking material accumulation and how those materials interact with one another to then make larger atoms, especially the more massive planets.

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gunnervi t1_iu322yk wrote

The closer you get to the sun -- or in this case, the protostar that became the sun -- the hotter it gets. Obviously. That's important because it means that when you're close to the sun, it's too hot for many molecules to stay solid, and they'll evaporate (or rather, sublimate). It's very difficult for forming planets to accrete gases, so planets that form close to the sun will generally be denser.

Outside a certain radius, it will be cool enough for water to form ice, and the average density of solid material will plummet. The moons of the gas giants, and Kuiper Belt objects like Pluto are much less dense than Earth because they're made of much more water than Earth, by mass. Planetesimals in this part of the solar system can even grow large enough to start accreting the gases in the forming solar system and grow to incredible masses.

Of course, formation is not the end of the story. Our solar system is not static, and the planets can radically change their position with time. There are many examples of Jupiter sized exoplanets that orbit their stars further in than Mercury!

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FerociousPancake t1_iu3sq82 wrote

If you’re further in than mercury you would have a good chance of being tidally locked right?

I wonder about mercury too since it has like no crust compared to the earth. I had heard one theory that mercury had a big collision and it stripped away most of that crust. Sucks mercury is so hard to get to. I wish we knew more about it.

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