why are all the planets around us sterile?

Answer 1

Too hot or too cold or too poisonous...is that simple enough an answer or too simple?

Answer 2

Well, in Mercury's case, it's because it's too small, but more importantly, it's too close to the sun, so life couldn't develop properly there.

As for Venus, scientists conclude that the core of the planet cooled down too fast, and there isn't enough rotation (a "day" on Venus is 243 Earth days, while it takes 225 Earth days to orbit the sun once. Yes, a "day" on Venus is longer than its "year"). Some say this is an example of runaway greenhouse effect (which they also might argue on global warming on Earth).

Mars is too small (only about half the size of Earth) and while I think it's in the "habitable zone" for life, its atmosphere is too thin and it's too cold to support life as we know it.

As for the gas giants, I don't think any life as we know it is there, because the pressure on those planets is intense (so intense that hydrogen, normally a vapor on Earth, is liquid on those planets). We also don't know for sure if there's any solid ground to stand on, since it's hard for us to observe them without getting nuked by the intense radiation they give off (even the probes we sent there don't do well against the radiation, and they break down after a few years of orbit around Jupiter, for example). An interesting trivia bit about Jupiter is that if it had more mass, it could've also became a star (but there's not enough mass to trigger the reaction needed to become a sun, meaning it's just not big enough). I think the reason why the 4 inner planets don't have large atmospheres the same way the outer planets do is because when the sun was young, it emitted a lot of solar wind, which pushed away a lot of the gases the planets were collecting (and there's a theory that the asteroid belt was originally supposed to form a planet, but Jupiter basically crushed and spread it before it could happen).

You have to wonder though, how Earth is such a perfect planet to support life, and the other ones aren't capable of doing it.

Answer 3

Different planets have different reasons. Having no atmosphere is pretty much a no brainer...that covers most of the moons in our solar system...and Mercury, which is likewise baked in the sun and frozen in shade. Pretty harsh conditions. For Mars, it has no magnetic field or ozone layer to shield it from sterilizing UV radiation from the sun. Robotic probes have pretty much verified that the top few inches of soil on Mars is sterile. However, Mars may have once had a magnetic field and if life developed long in the past, it could have moved into underground aquifers are into the rock itself. Venus is just hellishly hot...doubtful anything could survive that.

The gas giants are a bit of a mystery...could there be life in those clouds? We don't know. The Galileo probe dropped an atmospheric probe into Jupiter when it arrived...it found no organic compounds. It also found no oxygen in the particular place it dropped through...but we know there is some oxygen in other places because we have detected it. (Not that this oxygen would sustain life...but it shows that the probe might have missed other things too.) Ergo, it's still possible there are organic compounds eleswhere.

Answer 4

Well all the planets around the earth are the inner planets. Mercury,Venus,and Mars. The reason why the planets around us are sterile because we live within the distance of the sun.(otherwise known as the life zone or habitable zone).

Answer 5

We don't know that they are sterile for certain. We are basing this theory on the assumption that all life in the Universe will be like life as we know it or similar i.e. oxygen breathing, water being a necessity.

Answer 6

Some are too hot and some are too cold;
but like the 'infamous' porridge - our
planet is just right (with conditions that
permit liquid water and oxygen).

Answer 7

because the Earth is within the habitable zone of our star, the sun.