Where Would Earth-Like Planets Find Water?

astroengine writes "The term 'Earth-like worlds' is a vastly overused and hopelessly incorrect term that is popularly bandied about to explain some recent exoplanet discoveries. Although some of the distant small worlds being discovered by the Kepler space telescope may be of Earth-like size, orbiting their sun-like star in Earth-like orbits, calling those worlds 'Earth-like' gives the impression these alien planets are filled with liquid water. It turns out that we have only a vague idea as to where Earth got its water, and it will take a long time until we have any hint of this life-giving resource on worlds orbiting stars thousands of light-years away."

Comments

Steal from Star Trek.

[khasim]

How about a basic classification scheme for planets?
http://en.wikipedia.org/wiki/Class_M_planet
Except do it better. World size, composition, orbit, etc.

Then, instead of reporting about another "Earth-like" planet they could report on a class blah-blah-blah-blah planet that MAY be "Earth-like".

Re:Wish they would just knock it off with "earth-l

[Anonymous Coward]

The whole nonsense of even using the term "earth-like" is a joke, born of the press and PR-minded astronomers. Calling a planet "earth-like" implies way more than correlation with earth's size and it's orbit around the sun. There are so many characteristics which may well make the earth a very unique planet. It's not just the presence of water, either--it's also our magnetic field, the presence and effects of our moon, the nature of our core, etc. It could very well be that true earth-like planets are VERY rare in the universe.

Or it could be that we're _not_ so lucky, that these are fairly common, or turn out to be much less essential than we thought. Since we can't measure those remotely (yet), we have no way to stake a solid claim either way.

So what's wrong with "Earth-like" when referring to planets of which every parameter we _can_ remotely measure at present (thus all the ones we _know_ are scarce) match? Only illiterate fools would choose to infer similarities that we couldn't possibly know from that, and frankly they'll misunderstand no matter what terminology you use.

Re:Easy

[icebike]

That was my response as well. Whereever Oxygen and Hydrogen exist, the problem is NOT creating water. In fact, it's very likely that the largest source of water outside of the Earth in our Solar System is orbiting Saturn.

You may be right about the source being other moons. Comets are another potential source, Louis Frank published his theory in The Big Splash, but it never seemed to gain a lot of traction, even though the guys has a lot of credentials. It was generally disregarded, like so many other novel theories.

In the book he postulates that thousands of small fluffy snow-ball comets with no hard central core and which which don't really show up in radar or visually, deposit tons of water on the earth's atmosphere and the moon every year. He even had images in his book about impacts on the moon.

Re:Wish they would just knock it off with "earth-l

[Longjmp]

Wrong on both accounts.
There are actually twice as many even numbers than odd ones.
Proof:

Assume any even number "n", so
n * n = [even]
n * (n-1) = [even]
n * (n-2) = [even]

Now take any odd number "m":
m * m = [odd]
m * (m-1) = [even]
m * (m-2) = [odd]

So out of any two odd/even numbers you can generate twice as many even numbers compared to odd numbers.
q.e.d.

(and yes, for the non-maths out there, it is a joke)