Mars is one of the most fascinating planets in the solar system. It's the subject of a much exploration, and scientists have sent dozens of spacecraft there. Human missions to this world are currently in planning and might happen in the next decade or so. It may be that the first generation of Mars explorers are already in high school, or perhaps in college. If so, it's high time we learn more about this future target!
The current missions to Mars include the Mars Curiosity Lander, the Mars Exploration Rover Opportunity, the Mars Express orbiter, the Mars Reconnaissance Orbiter, the Mars Orbiter Mission, and Mars MAVEN, and the ExoMars orbiter.
Basic Information about Mars
So, what are the basics about this dusty desert planet? It's about 2/3 the size of Earth, with a gravitational pull just over a third of Earth's. Its day is about 40 minutes longer than ours, and its 687-day-long year is 1.8 times longer than Earth's.
Mars is a rocky, terrestrial-type planet. Its density is about 30 percent less than that of Earth (3.94 g/cm3 vs. 5.52 g/cm3). Its core is probably similar to Earth's, mostly iron, with small amounts of nickel, but spacecraft mapping of its gravity field seem to indicate that its iron-rich core and mantle are a smaller portion of its volume than on Earth. Also, its smaller magnetic field than Earth, indicates a solid, rather than liquid core.
Mars has evidence of past volcanic activity on its surface, making it a sleeping volcano world. It has the largest volcanic caldera in the solar system, called Olympus Mons.
Mars' atmosphere is 95 percent carbon dioxide, nearly 3 percent nitrogen, and nearly 2 percent argon with trace quantities of oxygen, carbon monoxide, water vapor, ozone, and other trace gases. Future explorers will need to bring oxygen along, and then find ways to manufacture it from surface materials.
The average temperature on Mars is about -55 C or -67 F. It can range from -133 C or -207 F at the winter pole to almost 27 C or 80 F on the day side during summer.
A Once-wet and Warm World
The Mars we know today is largely a desert, with suspected stores of water and carbon dioxide ice under its surface. In the past it may have been a wet, warm planet, with liquid water flowing across its surface. Something happened early in its history, however, and Mars lost most of its water (and atmosphere). What wasn't lost to space froze underground. Evidence of dried ancient lakebeds have been found by the Mars Curiosity mission, as well as other missions. The apparently history of water on ancient Mars gives astrobiologists some idea that life might have gotten a toehold on the Red Planet, but has since died out or is holed up beneath the surface.
The first human missions to Mars will likely occur in the next two decades, depending on how the technology and planning progresses. NASA has a long-range plan to put people on Mars, and other organizations are looking into creating Martian colonies and science outposts as well. Current missions in low-Earth orbit are aimed at learning how humans will live and survive in space and on long-term missions.
Mars has two tiny satellites which orbit very close to the surface, Phobos and Deimos. They could well come in for some exploration of their own as people begin their in-situ studies of the Red Planet.
Mars in the Human Mind
Mars is named for the Roman god of War. It probably got this name due to its red color. The name of the month March derives from Mars. Known since prehistoric times, Mars has also been seen as a god of fertility, and in science fiction, it is a favorite site for authors to stage stories of the far future.
Edited by Carolyn Collins Petersen.