Geoscience Reference
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light is blocked before it can dissociate water into hydrogen and oxygen. Because
little water vapor rises above the troposphere and the ozone layer is in the upper
stratosphere, little water is dissociated into hydrogen and oxygen.
The Earth's magnetic field is 31 T. Mars would require a similar magnetic
field intensity to similarly offset the effects of the solar wind at its distance further
from the Sun. The technology for inducing a planetary-scale magnetic field does not
currently exist.
The importance of magnetosphere has been brought into question. In the past,
Earth has regularly had periods where the magnetosphere changed direction, yet life
has continued to survive. A thick atmosphere similar to Earth's could also provide
protection against solar radiation in the absence of a magnetosphere.
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According to modern theorists, Mars exists on the outer edge of the habitable zone,
a region of the solar system where liquid water can exist, and so, where life (as
we know it) can exist. Mars is on the border of a region known as the extended
habitable zone where concentrated greenhouse gases could support the liquid water
on the surface at sufficient atmospheric pressure. Therefore, Mars has the potential
to support a hydrosphere and biosphere.
The lack of both a magnetic field and geologic activity on Mars may be a result
of its relatively small size, which allowed the interior to cool more quickly than
Earth's, though the details of such a process are still not well understood.
It has been suggested that Mars once had an environment relatively similar to that
of Earth during its earlier stage of development. Although water appears to have
once been present on the Martian surface, water appears to exist at the poles just
below the planetary surface as permafrost. On September 26, 2013, NASA scientists
reported that the Mars Curiosity rover detected abundant, easily accessible water
(1.5-3 wt%) in soil samples at the Rocknest region of Aeolis Palus in Gale Crater.
The soil and atmosphere of Mars contain many of the main elements needed for
life. Large amounts of water ice exist below the Martian surface, as well as on the
surface at the poles, where it is mixed with dry ice and frozen CO
2
.
Significant amounts of water are stored in the south pole of Mars, which, if
melted, would correspond to a planet-wide ocean 11 m deep. Frozen carbon dioxide
(CO
2
) at the poles sublimates into the atmosphere during the Martian summers, and
small amounts of water residue are left behind, which fast winds sweep off the poles
at speeds approaching 400 km/h (250 mph). This seasonal occurrence transports
large amounts of dust and water vapor into the atmosphere, giving potential for
Earth-like cirrus clouds.
Most of the oxygen in the Martian atmosphere is present as carbon dioxide
(CO
2
), the main atmospheric component. Molecular oxygen (O
2
) only exists in trace
amounts. Large amounts of elemental oxygen can be also found in metal oxides on
the Martian surface and in the soil, in the form of pernitrates. An analysis of soil
samples taken by the Phoenix lander indicated the presence of perchlorate, which
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