Danny Rasheed, age 12, of Nashua, N.H., for his question:
DOES IT RAIN ON OTHER PLANETS?
A planet's temperature, atmosphere, surface features, length of days and nights and other conditions depend on three things: the planet's distance from the sun, its atmosphere and the planet's rotation.
Scientists tell us that none of the other planets have the same conditions that can be found on earth. For this reason, rain as we know it most likely doesn't fall on other planets.
The earth is the only planet with a large amount of oxygen in its atmosphere, and oxygen is an important part of water.
Atmosphere is a mixture of the gases that surround a planet. You will find that the atmosphere of terrestrial planets the four nearest the sun, namely Mercury, Venus, Earth and Mars consist chiefly of carbon dioxide and nitrogen.
Helium, hydrogen, methane and ammonia make up most of the atmosphere of the major planets, namely Jupiter, Saturn, Uranus and Neptune.
Another reason why rain as we know it seems unlikely in other planets is because of temperatures. Temperature on the planet closest to the sun, Mercury, rises to about 625 degrees Fahrenheit. Pluto, more than 100 times as far from the sun as Mercury, probably has temperatures of more than 300 degrees below zero Fahrenheit.
Earth has an average temperature of 57 degrees Fahrenheit, the only planet within a range that is not extreme.
Many questions remain unanswered regarding the planets. Are there solid surfaces on Saturn, Uranus and Neptune or are the surface materials of these planets largely liquid or compressed vapor? Does any form of life exist on Mars?
They also ask why Venus, with an average surface temperature of 800 degrees Fahrenheit, is so very hot when it is surrounded by clouds that should reflect much of the sun's heat.
All of the planets move around the sun in the same direction. Also, each planet rotates as it revolves around the sun.
Planets vary greatly in size and in distance from the sun. The nine that travel around the sun are solid bodies of material that do not produce their own light and heat.
All nine of the planets together weigh less than a hundredth as much as the sun. The largest, Jupiter, is only about a tenth of the sun's diameter yet it is almost 30 times as large as Mercury.
The planets' rotation periods, or the time required to spin around once, range from less than 10 hours for Jupiter to 243 days for Venus. Our planet Earth rotates once every 24 hours.