Astronomy Questions (with Answers)

Why are comets are called dirty snowballs?

Comets are often described as "dirty snowballs" because the solid bit of a comet, called the nucleus, is made of water ice mixed with "dry ice" (solid carbon dioxide), and seems to be coated with a very black material that is rich in carbon. The ice is very dirty, with lots of rocky material mixed into it, which is where we get the "dirty snowballs" name!

What are asteroids? What are they made of?

Asteroids are space rocks. Asteroids are made of rock, metals and other elements. Some even contain water, astronomers say. Asteroids that are mostly stone sometimes are more like loose piles of rubble. Asteroids that are mostly iron are more, well, rock-solid.

Define solar system

Solar System is the collection of eight planets and their moons in orbit round the sun, together with smaller bodies in the form of asteroids, meteoroids, and comets.

Terrestrial Planets vs. Gas Giants

1. Gas giants have a helium and hydrogen based atmosphere, whereas Terrestrial planets have a more Carbon dioxide based atmosphere.

2. Gas giants have a lower temperature than Terrestrial planets.

3. Gas giants have rings (faint and noticeable) whereas Terrestrial planets do not have any rings at all.

4. The terrestrial planets are much closer to the sun; the gas giants are much further away from the sun.

Which are the most likely places in our solar system for life to exist (aside from Earth of course)?

The search for places where life might exist is usually driven by the search for liquid water - on Earth, where there's life, there's water. So we need to look at places that might still have liquid water, and outside of the Earth there are not too many of those. Many scientists think that life might once have existed on Mars, when it was warmer and wetter than it is today - if it did, it would very simple life-forms, like microbes, not the sort of aliens you see in films! There are some parts of Mars today where life might still exist, below the surface and sheltered from the intense cold and the radiation that the surface is exposed to - but we need to send scientists who can drill deep below the ground before we can really study that in detail. Some other places where we might look would be beneath the icy surfaces of some of the moons of Jupiter and Saturn. Jupiter has a moon called Europa that we think has a liquid water ocean hidden beneath a crust of ice that might only be a few hundred metres think in some places - and that ocean could be 200km deep.