Is Earth the only planet in our solar system that could
support life? The most Earth-like of the planets is
Mars, one of our closest planetary neighbors. Rotating
on its axis once every 24.5 hours, Mars's day is nearly
the same length as Earth's. Mars also experiences seasons,
due to the 28.7° tilt of its axis.
We have long been fascinated with the possibility of
life on Mars. Through early telescopes, astronomers
saw light and dark areas that they believed might be
continents and seas. In 1877, the Italian astronomer
Giovanni Schiaparelli observed what he thought were
linear features on Mars's surface, calling them "canali",
or channels. When this was mistranslated as canals,
many people pictured large artificial structures. Someone
had to have built these structures, they reasoned, so
they imagined the planet populated by intelligent lifethe
Martians. When the quality of telescopes improved sufficiently
to see Mars's surface, it was shown that these canals
did not exist.
In science fiction books and movies, Mars is home to
many fascinating creatures. So far, however, no evidence
of any kind of Martian life has been found. Scientists
continue to search for signs of life, current or in
the past, on Mars.
these views of Earth and Mars from space. The planets'
sizes are shown to scale. Click the image to see a larger
Mars: NASA/JPL/Malin Space Science Systems. Earth:NASA Goddard Space Flight Center; Image by Reto Stockli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes). Data and technical support: MODIS Land Group; MODIS Science Data Support Team, MODIS Atmosphere Group; MODIS Ocean Group.