a person living in a different country than the one in which he or she was born and who is not a legal citizen
Books and movies also tell stories about aliens on Mars.

to have a particular opinion about something
Some people believe there might be something living on Mars.

to find something for the first time
Many scientists want to discover a new kind of animal.

coming after three other things in a series
The fourth person to finish the race does not get a prize.

the ability to develop and change physically that separates plants and animals from objects that are not living
No life has been discovered on Mars yet.

the small red planet that is fourth in order from the sun and is nearest the Earth
mars is often called the "red planet" because it looks red.

a location, such as a building, point, or town
In winter on Mars, it can be much colder than even the coldest place on Earth.

a massive round object in space which moves around a star
We live on the planet Earth.

a machine controlled by a computer that is able to move and perform many of the same tasks as people can
Now, robots are on Mars looking for life.

to cause something to be moved from one place to another place, often electronically or by mail
He sends a letter to his friend every month.