
Alien Worlds Might Be Covered in Enormous Mountains - Thevet
http://www.theatlantic.com/science/archive/2016/06/the-enormous-mountains-of-alien-worlds/489101/?single_page=true
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antognini
A classic question in Order of Magnitude Physics classes is to calculate the
maximum height of a mountain that a planet can support. There are a couple of
solutions to this around the internet [1--2], but the main result is that the
maximum height is inversely proportional to the surface gravity. At constant
density, the surface gravity, in turn, is proportional to radius. So the
maximum height of a mountain is inversely proportional to radius and you would
expect that smaller planets have taller mountains.

You can take this to one extreme and ask how large an asteroid can be before
it becomes spherical under its own gravity. This essentially means that the
tallest mountain must be much less than the radius of the asteroid. If you
work out the math it turns out that the largest non-spherical asteroid should
be around a few hundred km in size, which agrees well with observations.

At another extreme you can perform this calculation for a neutron star.
Although the radius is very small (which would seem to imply that it can
support tall mountains), the density is much different from ordinary matter.
As a result, the tallest mountains a neutron star can support is on the order
of a few millimeters! Neutron stars are _extremely_ spherical. (More
correctly, due to spin, neutron stars are extremely spheroidal.)

[1]:
[http://www.phy.cuhk.edu.hk/phyworld/articles/mount_high/moun...](http://www.phy.cuhk.edu.hk/phyworld/articles/mount_high/mount_high_e.html)

[2]: [https://talkingphysics.wordpress.com/2011/09/08/how-high-
can...](https://talkingphysics.wordpress.com/2011/09/08/how-high-can-
mountains-be/)

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pavel_lishin
Would it be plausible for a mountain on an alien world to reach high enough to
aid in space exploration? High enough to make launches cheaper from its peak?

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methodover
It's hard to express how sad it makes me that I'll never see photos of the
surface of another inhabited world.

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manachar
Probabilistically, this is true, but think how amazing it is we have photos
take from the surface of such far away places like Mars, Titan, comets, etc.
Heck, the latest photos of Pluto are some of the most amazing things I've ever
seen.

It's conceivable that we will be able to send a probe to Europa that can drill
through the ice to sample an alien ocean and maybe even find life!

You can talk to people today who remember life before flight was really
around, and for whom the universe was mostly just a background to evening
activities. Every time we look out with more modern equipment we find the
universe is more and more vibrant.

Alien worlds inhabited by other intelligences than ours would be amazing
though.

~~~
paavokoya
One could consider our Mars rovers as life on other planets.. They don't have
"organic" (as in water based) cells but they are self-sustaining and active to
this day.. They communicate back to Earth and do what we tell them, which is
what most isolated lifeforms do in regards to their parents.

