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! Rotation period (length of day) 24 hours, 39 min, 35 sec (1.027 Earth days) |
! Poles tilted 25 degrees, creating seasons similar to Earth's |
! Atmosphere composed chiefly of carbon dioxide (95.3%), nitrogen (2.7%) and argon (1.6%) |
! Surface atmospheric pressure less than 1/100th that of Earth's average |
! Surface winds up to 80 miles per hour (40 meters per second) |
! Local, regional and global dust storms; also whirlwinds called dust devils |
! Surface temperature averages -53 C (-64 F); varies from -128 C (-199 F) during polar night to |
27 C (80 F) at equator during midday at closest point in orbit to Sun |
! Highest point is Olympus Mons, a huge shield volcano about 26 kilometers (16 miles) high and |
600 kilometers (370 miles) across; has about the same area as Arizona |
! Canyon system of Valles Marineris is largest and deepest known in solar system; extends more |
tops of surrounding plateaus |
! "Canals" observed by Giovanni Schiaparelli and Percival Lowell about 100 years ago were a |
visual illusion in which dark areas appeared connected by lines. The Mariner 9 and Viking missions |
of the 1970s, however, established that Mars has channels possibly cut by ancient rivers |
! Two irregularly shaped moons, each only a few kilometers wide |
! Larger moon named Phobos ("fear"); smaller is Deimos ("terror"), named for attributes personi- |
fied in Greek mythology as sons of the god of war |
Historical Mars Missions |
Mission, Country, Launch Date, Purpose, Results |
[Unnamed], USSR, 10/10/60, Mars flyby, did not reach Earth orbit |
[Unnamed], USSR, 10/14/60, Mars flyby, did not reach Earth orbit |
[Unnamed], USSR, 10/24/62, Mars flyby, achieved Earth orbit only |
Mars 1, USSR, 11/1/62, Mars flyby, radio failed at 106 million km (65.9 million miles) |
[Unnamed], USSR, 11/4/62, Mars flyby, achieved Earth orbit only |
Mariner 3, U.S., 11/5/64, Mars flyby, shroud failed to jettison |
Mariner 4, U.S. 11/28/64, first successful Mars flyby 7/14/65, returned 21 photos |
Zond 2, USSR, 11/30/64, Mars flyby, passed Mars but radio failed, returned no planetary data |
Mariner 6, U.S., 2/24/69, Mars flyby 7/31/69, returned 75 photos |
Mariner 7, U.S., 3/27/69, Mars flyby 8/5/69, returned 126 photos |
Mariner 8, U.S., 5/8/71, Mars orbiter, failed during launch |
Kosmos 419, USSR, 5/10/71, Mars lander, achieved Earth orbit only |
Mars 2, USSR, 5/19/71, Mars orbiter/lander arrived 11/27/71, no useful data, lander burned up |
due to steep entry |
Mars 3, USSR, 5/28/71, Mars orbiter/lander, arrived 12/3/71, lander operated on surface for 20 |
seconds before failing |
Mariner 9, U.S., 5/30/71, Mars orbiter, in orbit 11/13/71 to 10/27/72, returned 7,329 photos |
Mars 4, USSR, 7/21/73, failed Mars orbiter, flew past Mars 2/10/74 |
Mars 5, USSR, 7/25/73, Mars orbiter, arrived 2/12/74, lasted a few days |
Mars 6, USSR, 8/5/73, Mars flyby module and lander, arrived 3/12/74, lander failed due to fast impact |
Mars 7, USSR, 8/9/73, Mars flyby module and lander, arrived 3/9/74, lander missed the planet |
Viking 1, U.S., 8/20/75, Mars orbiter/lander, orbit 6/19/76-1980, lander 7/20/76-1982 |
Viking 2, U.S., 9/9/75, Mars orbiter/lander, orbit 8/7/76-1987, lander 9/3/76-1980; combined, |
the Viking orbiters and landers returned 50,000+ photos |
Phobos 1, USSR, 7/7/88, Mars/Phobos orbiter/lander, lost 8/88 en route to Mars |
Phobos 2, USSR, 7/12/88, Mars/Phobos orbiter/lander, lost 3/89 near Phobos |
Mars Observer, U.S., 9/25/92, lost just before Mars arrival 8/21/93 |
Mars Global Surveyor, U.S., 11/7/96, Mars orbiter, arrived 9/12/97, high-detail mapping through |
1/00, now conducting second extended mission through fall 2004 |
Mars 96, Russia, 11/16/96, orbiter and landers, launch vehicle failed |
Mars Pathfinder, U.S., 12/4/96, Mars lander and rover, landed 7/4/97, last transmission 9/27/97 |
Nozomi, Japan, 7/4/98, Mars orbiter, currently in orbit around the Sun; Mars arrival delayed to |
12/03 due to propulsion problem |
Mars Climate Orbiter, U.S., 12/11/98, lost upon arrival 9/23/99 |
Mars Polar Lander/Deep Space 2, U.S., 1/3/99, lander and soil probes, lost on arrival 12/3/99 |
Mars Odyssey, U.S., 3/7/01, Mars orbiter, arrived 10/24/01, currently conducting prime |
mission studying global composition, ground ice, thermal imaging |
Mars Express/Beagle 2, European Space Agency, 6/2/03, Mars orbiter/lander, due to enter orbit 12/03, |
landing 12/25/03 |
Mars: The Water Trail |
Thirty-eight years ago, on the eve of the first spacecraft flyby of Mars, everything we |
knew about the Red Planet was based on what sparse details could be gleaned by |
peering at it from telescopes on Earth. Since the early 1900s, popular culture had |
been enlivened by the notion of a habitable neighboring world crisscrossed by canals |
and, possibly, inhabited by advanced lifeforms that might have built them -- whether |
friendly or not. Astronomers were highly skeptical about the canals, which looked |
more dubious the closer they looked. About the only hard information they had on |
Mars was that they could see it had seasons with ice caps that waxed and waned, |
along with seasonally changing surface markings. By breaking down the light from |
Mars into colors, they learned that its atmosphere was thin and dominated by an |
unbreathable gas known as carbon dioxide. |
The past four decades have completely revolutionized that view. First, hopes of a |
lush, Earth-like world were deflated when Mariner 4's flyby in 1965 revealed large |
impact craters, not unlike those on Earth's barren, lifeless Moon. Those holding out for |
martians were further discouraged when NASA's two Viking landers were sent to the |
surface in 1976 equipped with a suite of chemistry experiments that turned up no con- |
clusive sign of biological activity. Mars as we came to know it was cold, nearly airless |
and bombarded by hostile radiation from both the Sun and from deep space. |
But along the way since then, new possibilities of a more hospitable martian past have |
emerged. Mars is a much more complex body than Earth's Moon. Scientists scrutiniz- |
ing pictures from the Viking orbiters have detected potential signs of an ancient coast- |
line that may have marked the edges of a long-lost sea. Today's Mars Global Surveyor |
and Mars Odyssey orbiters have revealed many features that strongly appear to have |
been shaped by running water that has since disappeared, perhaps buried as layers of |
ice just under the planet's surface. |
Although it appears unlikely that complex organisms similar to Earth's could have exist- |
ed in any recent time on Mars' comparatively hostile surface, scientists are intrigued by |
the possibility that life in some form, perhaps very simple microbes, may have gained a |
foothold in ancient times when Mars may have been warmer and wetter. It is not |
unthinkable that life in some form could persist today in underground springs warmed |
by heat vents around smoldering volcanoes, or even beneath the thick ice caps. To |
investigate those possibilities, scientists must start by learning more about the history |
of water on Mars -- how much there was and when, in what form it existed, and how |
long it lasted. |
One of the most promising ways to answer those questions is to look at the diverse |
clues that water has left on Mars. Besides the water-carved landforms visible for |
decades from orbiting spacecraft, many details of the story of water on the Red Planet |
are locked up in the rocks littered across its surface. Rocks are made up of building |
blocks known as minerals, each of which tells the story of how it came to be a part of a |
any given rock. Some types of minerals, for example, are known to form on Earth only |
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