On January 15, 2004, the NASA rover Spirit rolled onto the surface of Mars. For 90 days, the six-wheeled vehicle took pictures of the Martian landscape, gathered soil samples for geological analysis, and assessed atmospheric conditions. Spirit went on to function 20 times longer than expected, but on May 1, 2009, the rover became stuck in soft soil and has not moved since.

The rover is powered by solar panels and is equipped with magnets, a thermometer, a navigation camera, and a small drill for grinding samples of Martian rock. As of 2009, the rover had traveled almost 8 kilometers (5 miles) across the Martian surface. Spirit has made a number of important discoveries, including the existence of dust devils (small tornadoes) on Mars and the possibility that water may have existed on Mars at some point in the past.

assess
Verb

to evaluate or determine the amount of.

atmosphere (atm)
Noun

(atm) unit of measurement equal to air pressure at sea level, about 14.7 pounds per square inch. Also called standard atmospheric pressure.

geologic
Adjective

having to do with the physical formations of the Earth.

Noun

the geographic features of a region.

magnet
Noun

material that has the ability to physically attract other substances.

Mars
Noun

fourth planet from the sun, between Earth and Jupiter.

NASA
Noun

(National Aeronautics and Space Administration) the U.S. space agency, whose mission statement is "To reach for new heights and reveal the unknown so that what we do and learn will benefit all humankind."

Noun

art and science of determining an object's position, course, and distance traveled.

rock
Noun

natural substance composed of solid mineral matter.

rover
Noun

vehicle that remotely explores a region, such as the surface of a moon, planet, or other celestial body.

soil
Noun

top layer of the Earth's surface where plants can grow.

solar panel
Noun

group of cells that converts sunlight into electricity.

Noun

device that measures temperature.

tornado
Noun

a violently rotating column of air that forms at the bottom of a cloud and touches the ground.