Mars
(TFS) - Mars is the fourth planet from the Sun and the seventh
largest
Planet
Profile
orbit: 227,940,000
km (1.52 AU) from Sun
diameter: 6,794
km
mass: 6.4219e23
kg
Mars is called the red planet because of the reddish
dust which the wind lifts on its desert slide. It is a dry and cold planet
where the temperature can go down to -60 ° C, and blow violent storm. Its
surface is covered with volcanoes, some of which are giant.
It takes 24h 37 min to orbit a round itslef. In 1976, viking1 and 2 overflew Mars and deposited modules on its surface. Other expeditions were conducted to bring back samples of rocks that might well reveal us if there has already been life on Mars.
It takes 24h 37 min to orbit a round itslef. In 1976, viking1 and 2 overflew Mars and deposited modules on its surface. Other expeditions were conducted to bring back samples of rocks that might well reveal us if there has already been life on Mars.
Mars Red Terrain
Mars' orbit is significantly elliptical. One result of
this is a temperature variation of about 30 C at the subsolar point between aphelion and perihelion. This has a major influence on Mars' climate. While
the average temperature on Mars is about 218 K (-55 C, -67 F), Martian surface
temperatures range widely from as little as 140 K (-133 C, -207 F) at the
winter pole to almost 300 K (27 C, 80 F) on the day side during summer.
Though Mars is much smaller than Earth, its
surface area is about the same as the land surface area of Earth
Terrain of Mars
Structure
Mars has some of the most highly varied and
interesting terrain of any of the terrestrial planets, some of it quite
spectacular:
Olympus Mons: the largest mountain in the Solar System rising 24 km
(78,000 ft.) above the surrounding plain. Its base is more than 500 km in diameter
and is rimmed by a cliff 6 km (20,000 ft) high.
Olympus Mons
Tharsis: a huge bulge on the Martian surface that is about 4000 km across and 10 km high.
Valles Marineris: a system of canyons 4000 km long and from 2 to 7 km deep (top of page);
Valles Marineris
Hellas Planitia: an impact crater in
the southern hemisphere over 6 km deep and 2000 km in diameter.
Hellas Planitia
Much of the Martian surface is very old and
cratered, but there are also much younger rift valleys, ridges, hills and
plains.
The southern hemisphere of Mars is predominantly
ancient cratered highlands somewhat similar to the Moon. In contrast, most of
the northern hemisphere consists of plains which are much younger, lower in
elevation and have a much more complex history. An abrupt elevation change of
several kilometers seems to occur at the boundary. The reasons for this global
dichotomy and abrupt boundary are unknown.
Water on Mars?
Currently, there is no water on Mars in the liquid
state, nor vapor in the atmosphere, which is composed mainly of carbon dioxide.
But after missions sent to Mars, we know that the
water had existed there, 4 billion years ago.
There is very clear evidence of erosion in many places
on Mars including large floods and small river systems. At some time in the
past there was clearly some sort of fluid on the surface. Liquid water is the
obvious fluid but other possibilities exist. There may have been large lakes or
even oceans; the evidence for which was strenghtened by some very nice images
of layered terrain taken by Mars Global Surveyor and the mineralology results from MER Opportunity. Most of these point to wet episodes that
occurred only briefly and very long ago; the age of the erosion channels is
estimated at about nearly 4 billion years. However, images from Mars Express
released in early 2005 show what appears to be a frozen sea that was liquid
very recently (maybe 5 million years ago). Confirmation of this interpretation
would be a very big deal indeed! (Valles Marineris was NOT created by running
water. It was formed by the stretching and cracking of the crust associated
with the creation of the Tharsis bulge.)
Compared to Earth
Early in its history, Mars was much more like Earth.
As with Earth almost all of its carbon dioxide was used up to form carbonate
rocks. But lacking the Earth's plate tectonics, Mars is unable to recycle any
of this carbon dioxide back into its atmosphere and so cannot sustain a
significant greenhouse effect. The surface of Mars is therefore much colder
than the Earth would be at that distance from the Sun.
Life on Mars?
Recent observations with the Hubble Space Telescope
have revealed that the conditions during the Viking missions may not have been
typical. Mars' atmosphere now seems to be both colder and dryer than measured
by the Viking landers (more details from STScI).
The Viking landers performed experiments to determine
the existence of life on Mars. The results were somewhat ambiguous but most
scientists now believe that they show no evidence for life on Mars (there is
still some controversy, however). Optimists point out that only two tiny
samples were measured and not from the most favorable locations. More
experiments will be done by future missions to Mars.
Mars' Satellites
SBB
soucre: http://nineplanets.org/mars.html
