The newly arrived Trace Gas Orbiter is just the latest in a
long line of Mars probes. Last week we discussed the first decade of the
robotic exploration of Mars. I discussed the early attempts by both the Americans
and Russians to reach the red planet, culminating in the observations of the
Mariner Probes and the short lived landing attempt by Mars 3.
Both space agencies were keen to get more information from
Mars, and so several missions were dispatched throughout the 1970s. The USSR
didn’t have much luck with its landing attempts. The Mars 6 lander
crashed, while Mars 7 missed the planet entirely and is now in orbit around the
sun. However the Americans were about to land not one but two probes on the martian surface.
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| Locations of all Mars landing sites past and future, as well as the crash sites of the unsuccessful landers. |
The Viking Era
In 1975 the two Viking landers
touched down on Mars. These landers survived their descent and remained
operational for considerably longer than a few seconds, making Viking 1 the spacecraft
to successfully land on Mars. Both Viking missions consisted of a lander and an
orbiter. The landers began studying the environment on the surface, while the
orbiters recorded thousands of images, produced detailed “mosaics” of the planets
entire surface.
The landing sites for the Viking probes were Chryse
Planitia, and Utopia Planitia, both in the northern lowlands of Mars. The
landers carried a variety of instruments to study the environmental conditions
and meteorology of Mars. They also had a life detection experiment, although
the results of this proved inconclusive they did give us insights into the
chemical processes taking place within the martian soil. The Viking 1 lander
remained operational for over two thousand days, setting a record that wouldn’t
be surpassed for decades.
The 80’s and 90’s
Mars missions became less frequent throughout the subsequent
decades. The USSR attempted to reach Phobos, Mars’ largest moon twice in 1988,
but both missions failed. While the Americans had steadily improved at sending
things to Mars the Russian space agency had entered a string of bad luck which
endures to this day. Almost a decade later the Russian Mars ’96 probe also met
with failure. The Americans had lost contact with their Mars Observer spacecraft
in 1993, resulting in a decades long gap between successful Mars missions.
This sparse period was to end in 1997 which marked the arrival
of the next American orbiter; the Mars Global Surveyor (MGS). This spacecraft
was designed to map the planet in unprecedented detail. It would remain in
operation until 2006, returning far more data than all of the previous missions
combined. MGS provided unprecedented detail
of the martian surface, detecting features such as gullies and debris flows which
are indicative of very recent geological activity. By building up a global
dataset over many years the MGS produced an unprecedented record of martian
weather systems.
The late 90’s also marked the arrival of the Mars Pathfinder
mission. This American lander was a major milestone as it was the first time a
rover had been landed on Mars. Pathfinder, and its Sojourner rover were
intended primarily as a technology demonstration. However like many spacecraft
it massively exceeded its mission parameters returning tens of thousands of
images. The technology used in the sojourner rover paved the way for the Mars
Exploration Rovers of the following decade.
1998 marked the first time that a country other than NASA
and the USSR sent a probe to Mars. the Japanese Nozomi mission was a failure.
It had been intended to go into orbit around Mars, but orbital insertion
failed.
The success of Mars Pathfinder was followed by a string of
failures for NASA, with the loss of the Mars Climate Orbiter and Mars Polar
lander spacecraft. Despite constant improvements in technology and expertise, getting
to Mars is still extremely difficult.
The 21st century
The early 2000s got off to a good start with the launch of
the American Mars Odyssey orbiter in 2001. 2003 then saw the launch of both the
European Space Agency’s Mars Express and the NASA Mars Exploration Rovers. These
four missions have proved to be some of the most successful in the history of
Mars exploration. Both MER rovers were intended to operate on the surface for
90 “sols”. A sol is a martian solar days and these are 24 hours and 39 minutes
long, so the mission was supposed to last for several months. This would have
allowed the rovers to travel up to a kilometre and survey a much larger area
than a stationary lander would have been able to.
Both MER rovers massively exceeded these expectations. The
MER Spirit rover operated until 2010, traveling almost eight kilometres. The MER
Opportunity Rover is still operational at the time of writing, and has currently traveled 43,436.19 metres according to the mission
website. These rovers, and the instruments they carry have provided years of
information about the geology of the regions through which they have traveled
and provided an invaluable array of “ground truth” observations. This has
provided vital context for the analysis of more numerous satellite images.
And the satellite data has become
extremely numerous. Mars odyssey is expected to continue to function until at
least 2025, and is currently serving a communications relay for the Curiosity
Rover, as well as returning data from its remote sensing instruments. Mars
Express is also still operational, and played a key role in last week’s landing
attempt.
Several more missions have followed over the last decade. The
mars reconnaissance Orbiter was launched in 2005 and continues to survey the
martian surface, being heavily involved in landing site selection for future
surface missions. The Phoenix lander was launched in 2007 and landed high on
the northern plains. It returned lots of valuable information about the
composition of martian ground ice at the high northern latitudes.
The Mars Science Laboratory Curiosity Rover was landed in
2012 and has so far traversed more than 11 kilometre. It has studied the
geology of its landing site in unprecedented detail and will continue to do so
for some time. More recent arrivals include the American Mars Atmosphere and Volatile Evolution (MAVEN)
Mission and the Indian Mars Orbiter
Mission, both of which arrived at Mars in 2014. The Mars Orbiter mission is India’s first
interplanetary craft, and makes them the fourth space agency to reach Mars
successfully.
We really are living
in a golden age of Mars exploration.
Many of the more recent probes will
continue to operate for years to come, returning valuable information about the
environment, geology and weather of the red planet. With each new mission the
range and variety of instruments we have around Mars increases and more landing
sites are added to the list of places which have been visited by our machines.
A lot of people are
keen to send humans to Mars, and this would be a useful thing to do. But I’d
argue that the best thing we can do is keep new satellites and landers coming,
so that as the older instruments are retired we continue to have good coverage
of the red planet, and can continue the important work of trying to understand this
fascinating world.
References and Further Reading
Map of all Mars landing sites, including failed attempts andplanned missions. By Emily Lakdawalla, Licensed under a Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 Unported License.
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