Esther Keller, age 14, of Willingboro, N.J., for her question
HOW LONG IS A DAY ON MARS?
Mars is the fourth closest planet to the sun and the next planet beyond the Earth, which is third closest. As Mars orbits the sun, it spins on its axis, an imaginary line through its center. Mars rotates once every 24 hours and 37 minutes, which is the length of a day on Mars Earth rotates once every 23 hours and 56 minutes.
The diameter of Mars is about 4,200 miles, a little over half that of the earth. Pluto and Mercury are the only planets smaller than Mars. Mars travels around the sun in an elliptical or oval shaped orbit. Its distance from the sun varies from about 155 million miles at its farthest point to about 128 million miles at its closest. Mars takes about 687 Earth days to go around the sun, which is the length of a year on Mars. This compares with about 365 days for Earth to orbit the sun
Two small satellites or moons travel around Mars. The closer and larger one, named Phobos, is about 5,800 miles from the center of Mars. Its diameter is about 14 miles at its Equator and 11 miles from pole to pole. It travels around Mars once every seven and a half hours.
Deimos the smaller satellite, is about 14,600 miles from Mars' center and circles the planet once about every 30 hours. Deimos has a diameter of about six miles. An American astronomer named Asaph Hall discovered both satellites in 1877.
Scientists tell us that the surface conditions on Mars are more like the Earth's than are those of any other planet. But the plants and animals of Earth could not live on Mars. The temperature on Mars averages about minus 80 degrees Fahrenheit and there is a scarcity of liquid water and oxygen.
The Martian atmosphere is thinner and contains fewer gases than that surrounding the Earth. It consists chiefly of carbon dioxide, with small amounts of nitrogen, argon and oxygen. Mars has about one hundredth the atmospheric pressure found on Earth.
The tilt of Mars' axis causes the sun to heat the planet's northern and southern halves unequally, resulting in seasons and temperature changes. The seasons on Mars last about twice as long as those on Earth because Mars takes almost twice as long to go around the sun as Earth does.
Temperatures on Mars are generally lower than those on Earth because Mars is farther from the sun than Earth is. There is a wide variation between daytime and nighttime temperatures.
While the average temperature for the entire planet is about minus 80 degrees Fahrenheit,~the daytime temperature near Mars' Equator may rise as high as 70 degrees Fahrenheit. Astronomers estimate the average nighttime temperature on Mars to be about minus 150 degrees Fahrenheit.
Mars is about four fifths as dense as the Earth and the mass of Mars is only about a tenth that of the earth.