Earth and Mars

Earth and Mars

. This composite image demonstrates the relative size, similarities and main difference of Earth (left) and Mars (right). Mars is about half the size of the Earth. Both planets exhibit white clouds and polar caps. Bluish-white clouds of water ice hang above volcanoes on Mars (right center left) and large dark areas extend across its red surface (right - top right). The residual north polar cap on Mars (right top) is made of water ice, and is circled by dark dunes of sand and dust. The Earth also has clouds and polar caps composed of water ice. However, about 75 percent of the Earth is covered with oceans, while liquid water cannot now exist for long times on Mars. The Earth image was taken from the Galileo spacecraft in December 1990, and the Mars image was acquired by the Mars Global Surveyor in April 1999. (Courtesy of NASA and JPL (left and right) and Malin Space Science Systems (right).)

Copyright 2010, Professor Kenneth R. Lang, Tufts University