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Student 3: Low Merit
Planets where life could be found:
Mars
There is a large amount of evidence to suggest that there was once water on Mars. Satellite
images or Mars show that there is a network of river-like channels scattered across the
surface of Mars which may have once contained running water, either on the surface or just
underground.
For liquid water to be present on Mars today the atmosphere would have to be thicker and
the temperature hotter. Today the average temperature on mars is -63°C, liquid water only
exists above 0°C. The most likely place for water to exist is underground or at the poles.
The only obvious source of energy on Mars is the sun. If there were life on Mars it would
likely take the form of plants or organisms that rely on solar radiation to provide energy. The
soil on Mars has been tested to see if it contains any of the elements required for metabolic
action. Unfortunately nothing has been found, so the prospect of complex life on Mars today
is unlikely.
Titan
Very close observations of Titan have found traces of water vapour. This water vapour has
possibly been transferred to Titan from the distant icy rings of Saturn. Titan is very similar
to an ancient Earth, giving us reason to believe that there is a great possibility of life on
Titan. However, the highest surface temperature recorded on Titan is -100°C, which means
there is no possibility of liquid water on the surface, one of the fundamental factors in
sustaining life. Titan’s surface is hidden under a layer of methane clouds, but there have
been sightings of both light and dark areas on Titan’s surface which could be due to frozen
continents or hydrocarbon lakes. It appears that Titan’s surface is mostly covered with ice,
silicate rocks and minor lakes.
The features of Titan are very close to that of a young Earth. Titan contains the elements
that organisms require to metabolise. There is oxygen in the form of carbon monoxide and
carbon dioxide. A thick layer of methane clouds covers the surface, with organic compounds
raining onto the surface. It is possible that life could exist there.
Europa
Europa is one of Jupiter’s moons and is completely ice covered. Several kilometres below the
ice may be oceans of liquid water. This water forms because the gravity of Jupiter pulls the
crust of Europa causing heat which melts the ice. Primitive life could exist in that ocean.
Also, hydrothermal vents may exist on the ocean floor and organisms could live around
them, feeding off the chemicals that are released there such as hydrogen sulphide.
Observations have also shown that Europa’s atmosphere is made up mainly of oxygen which
has been formed from cosmic rays hitting the ice and breaking it down to oxygen and
hydrogen.
Extremophiles
An extremophile is an organism that is able to survive and thrive in extreme conditions that
complex organisms could not. They are many bacteria or Archaea, a primitive form of
bacteria.
Bacteria have been found living in hot geothermal pools at temperatures of 1200 Celsius.
They also have been found deep underground, in highly alkaline or salty lakes, or in
conditions of high radiation. Many extremophiles don’t need sunlight. This is an interesting
discovery as it means that it is possible for life to survive without the use of the sun as an
energy source. This means that even if the sun does not reach a distant planet, there is still
the possibility of primitive life forms living there.
Archaea
Archaea are a group of single celled organisms that can live in pretty much any conditions,
such as volcanic hot springs, soils, oceans and marshlands. They have been found in
extreme conditions such as very salty lakes (halophiles), very hot water such as over 80 0C
(thermophiles) and high acidity such as below pH 2 (acidophiles).
Archaea may be the types of organisms that could be found on other planets or moons
because of their ability to live in extreme environments. Some extremophile habitats are
similar to those on Mars, and micro-organisms could travel there on meteorites.
The Possibility of Extra-Terrestrial Life
There may be life on other planets or moons but it will be primitive life. The most likely life
forms to exist are extremophiles and Archaea. These organisms are micro-prganisms that
can withstand extreme environments, like thermal vents of Europa’s underground oceans.
They are extremely primitive life forms.
Mars, Titan and Europa all have conditions that enable primitive forms of life to survive
there. Europa’s underground oceans are fantastic places for extremophiles to thrive, they
provide liquid water, energy may be able to be obtained from thermal vents and the
environment is appropriate for several species of extremophiles to live in. The same can be
said for the surface of Titan, which provides water, in the form of ice, and energy in the form
of organic compounds. Extremophiles can adapt to most environments, so they would find
no problem living on the surface of a barren planet.
There is life in every corner of the Earth, even in places scientists never believed possible.
Therefore, it is completely possible for life to exist outside of the Earth.