for Life on Mars
The Life Test Experiments
the popular imagination, Mars has been the favored place for alien
life since the nineteenth century. By the time the
spacecraft arrived at Mars in the 1960's, many
of the general public were expecting to see a planet teeming with
plant and animal, if not intelligent, life. They were sadly
disappointed. Scientists, however, soon realized that while
advanced life - animal and plant-like entities - would be extremely
unlikely, there was more reason to think that microbial or simple
life might exist on the Red Planet, or at least may have existed
there in the past. The photographs from the Mariner series
of spacecraft, ( Mariner
7 and Mariner
9) showed evidence that water once flowed in abundance on
the Martian surface. Vast river systems, flooded plains
and even ocean basins were in evidence.
But these were clearly all
dry at the present time. No sign of liquid water, or what
happened to it. Planetary scientists speculate that
it is either concentrated at the polar caps as ice, it is frozen
below the Martian surface as permafrost and hidden by overlaying
dust and soil, or that it has evaporated or otherwise lost into
it was thought that if life existed it may not be currently active,
but dormant and could be revived given the right conditions -
for example heat and nutrients. Alternatively, dead life
in the form of fossils may be present on Mars. It was speculated
that these could be found in rock formations, but would most likely
be very small - microscopic, in fact. Viewing such specimens
would require microscopes.
first successful soft-landings by the Viking
spacecraft carried out a series of tests for life,
and these have been somewhat controversial ever since. The
official view, and the one to which most scientists currently
subscribe, is that the tests were negative or at best inconclusive.
since the Viking missions, there has been something of a revolution
in our understanding of life and life processes. It is now
accepted that microbial life can exist in what we think of as
the most inhospitable of environments (see Extremophiles).
Mars is one such environment and there
has been an unofficial re-examination of the Viking data over
the past few years. An interesting question to ponder
is - how we would interpret the Viking results if they were new
first Viking lander produced positive results but the second produced
no results, but it is claimed that inorganic peroxides could also
produce positive results in the test. The official conclusion
was that peroxides were present on the Martian surface.
The NASA scientist who designed the tests, Dr
Gilbert Levin, still maintains that the first test at
least was positive (see A
lesson from Huxley). Had the tests been carried out
on Earth and the same results been obtained, then the inevitable
conclusions would have been: yes! Life exists here!
up The Viking Mars
Mission Life Experiment
up Possible Habitats
for Life on Mars
up First Contact
- Design a spacecraft for a life detection mission
Earth from space....
Life for the 'Mars Rock"
Mars Links page
Scientist Magazine Mars links
Life on Mars I
Life on Mars II
to Mars - Children's page
Next Generation of Spacecraft
1997 NASA successfully landed the Pathfinder
probe and its mini rover Sojourner
on Mars, and opened the way for a new phase of Mars exploration.
Pathfinder was a great success and was followed by Mars
Global Surveyor, which despite some early mishaps has produced
spectacular results from its imaging system. In September
- Climate Orbiter arrived in the vicinity of Mars, but was
lost through mistakes in its orbital control calculations.
of these missions was designed to search specifically for life
signs, but the next mission Mars
- Polar Lander was designed with life experiments on board.
This was due to touch down on Mars in December 1999, but as
with its predecessor, it was lost. Future
NASA missions include Mars
2003 and Mars 2005 Of these, the last two are sample
return missions and will require special precautions
against the possible biological contamination of Earth by
Agency is also planning a Martian
Mission for 2005 to search for life.
© J Hodges, 1999
European Space Agency has
a Mars mission under development Mars
Express. It includes a lander vehicle called Beagle
2 which will touch down on the Red Planet some time around 2004.
Beagle is named after the ship that took Charles
Darwin on his voyage of discovery that led to "The
Origin of the Species" and the theory of evolution.
Its mission is to search for life in the Martian soil. It
will be equipped with cameras, a drilling arm, and spectroscopes
for chemical and mineral analysis. Soil samples will be collected
from below the surface, at depths safe from solar radiation and
the harsh oxidizing conditions above ground. Samples will
be analyzed for the presence of organic molecules, and if any are
found their elemental isotopes and chirality will be investigated.
Chain Reaction (PCR)
is used to copy single pieces of DNA
and reproduce them, virtually as required. PCR is one of the
most versatile and powerful techniques available to the biologist,
yet it was invented only in 1983, by Dr Kary Mullis, who was joint
winner of the Nobel Prize for Chemistry in 1993.
speedy multiplication process - called amplification - enables identical
quantities of DNA material to be produced in a short time.
The process is easy to carry out and highly reliable.
is in regular use as a forensic investigation aid, now used in both
criminal and civil legal actions. It has also changed evolutionary
biology into a science supported by excellent experimental evidence.
The historic relationships between species can now be worked out,
with a high degree of accuracy.
is a technique that will be extremely useful in the search for life
on Mars. When the Viking
missions landed the technique was still seven years from being invented.
But now NASA scientists at the Ames Research Center in San Jose,
are working at developing the technique for use on Mars robot explorers.
One is Rocco
Mancinelli, a microbial ecologist/exobiologist working through
the SETI Institute.
technique that is being developed uses differential
thermal analysis coupled with gas
chromatography. Tests and equipment development
have been carried out using organisms in Yellowstone National Park
and the Antarctic. It is assumed that if they exist, Martian
microbes will be similar to these organisms and will behave in much
the same way. One of the more advanced methods of analysis
that will be used is PCR, and ways to use the technique on a Mars
robot lander are being devised.
The Heck is PCR?
Spectroscopy offers new opportunities in trying to find out what
things are made of. It uses light reflected off (or in the
case of a star given off by) an object to reveal its chemical make-up.
does this work? The reflected light that comes
off an object has a particular color, or bands of color if we break
the light into its color components with a prism. If we now
shine the light through a small slit (known as a diffraction grating)
and study the colors very closely we will see that there are tiny
black lines and bright lines in the colors. It looks like
a shopping bar-code and in fact, it can be used like a bar code
too. Every chemical produces a unique set of lines and if
you know the lines, you can identify the chemical.
only does this work for light, it works for X-rays and Gamma rays.
With these we can not only look at the surface of an object, we
can look inside it and find out what chemicals are in there.
This works for organic chemicals as well as rock, gas or any material.
Also in some cases, the spectrometer does not have to be very near
the object being examined.
are now essential pieces of equipment on planetary explorer and
lander spacecraft. The image (left) of the rock Yogi
and the Sojourner robot shows a spectrometer being held to the rock
by the robot rover.
going to Mars is not the only way to search for Martian life. There is
an alternative approach...
All images NASA, unless shown
1999 Satellite Events Enterprises Inc.