Geoscience Reference
In-Depth Information
Space colonization will facilitate harvesting the solar system's energy and material
resources.
In many respects, Mars is the most Earth-like of all the other planets in the solar
system. It is thought that Mars once did have a more Earth-like environment early
in its history, with a thicker atmosphere and abundant water that was lost over the
course of hundreds of millions of years. Given the foundations of similarity and
proximity, Mars would make one of the most efficient and effective terraforming
targets in the solar system.
Ethical considerations of terraforming include the potential displacement of
indigenous life, even if microbial, if such life exists.
8.8.2.2
Challenges and Limitations
The Martian environment presents several terraforming challenges to overcome, and
the extent of terraforming may be limited by certain key environmental factors.
Low Gravity
The surface gravity on Mars is 38 % of that on Earth. It is not known if this is enough
to prevent the health problems associated with weightlessness. Additionally, the low
gravity (and thus low escape velocity) of Mars may render it more difficult for it to
retain an atmosphere when compared to the more massive Earth and Venus. Earth
and Venus are both able to sustain thick atmospheres, even though they experience
more of the solar wind that is believed to strip away planetary volatiles. Continuing
sources of atmospheric gases on Mars might therefore be required to ensure that an
atmosphere sufficiently dense for humans is sustained in the long term.
Countering the Effects of Space Weather (Cosmic Rays)
Mars lacks a magnetosphere, which poses challenges for mitigating solar radiation
and retaining atmosphere. It is believed that fields detected on Mars are remnants of
a magnetosphere that collapsed early in its history.
The lack of a magnetosphere is thought to be one reason for Mars' thin
atmosphere. Solar-wind-induced ejection of Martian atmospheric atoms has been
detected by Mars-orbiting probes. Venus, however, clearly demonstrates that the
lack of a magnetosphere does not preclude a dense atmosphere.
Earth abounds with water because its ionosphere is permeated with a magneto-
sphere. The hydrogen ions present in its ionosphere move very fast due to their
small mass, but they cannot escape to outer space because their trajectories are
deflected by the magnetic field. Venus has a dense atmosphere, but only traces of
water vapor (20 ppm) because it has no magnetic field. The Martian atmosphere also
loses water to space. Earth's ozone layer provides additional protection. Ultraviolet
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