10 photos that tell the story of Mars exploration

1. Holy gigapixels!

Curiosity Rover in Gale Crater. Via 360cities.com

Curiosity rover in Gale Crater. Via 360cities.net

This is technically cheating as following this link takes you to several gigapixel images of Mars that you can zoom and pan around, but they’re so amazing hopefully you can forgive me. These incredibly detailed images from the martian surface reveal the landscape and geology of the planet to a resolution that would have been unimaginable to previous generations of researchers. They reveal distinctive landforms that tell us about the history of the planet and its potential to have hosted life in the past. Imaging allows Curiosity to study its route and for the science team to locate points of interest that the rover can then use its other instruments to study. It is inevitable that not every point of interest can be visited but having such good photos means a lot of analysis can still be done. In the years and decades to come images and data from Curiosity rover will still be used for new scientific discoveries.

2. In the beginning.

Olympus Mons imaged by Mariner 9.

Olympus Mons imaged by Mariner 9. Via http://www.pianeta-marte.it/

In the ancient times known as the 1970s Mariner 9 became the first spacecraft to orbit another planet. The photo mosaic above might not look like much but it was part of a set of images that revolutionised Mars Science. When the spacecraft arrived at Mars the planet was covered in a dust storm but as Mariner 9 continued to orbit the dust settled and images sent back to Earth revealed massive volcanoes, huge canyons and smooth plains as well as ancient channels that looked like river systems on Earth. The first few spacecraft sent to Mars had been flyby missions that had unfortunately managed to photograph only ancient cratered highlands that looked like the lunar surface. These initial observations had been incredibly depressing to those hoping that Mars hosted life. However, Mariner 9’s photographs revealed that Mars had likely been a wet and volcanically active world for a significant amount of time in its past. Dynamic conditions that might have made life possible and made Mars science seem much more exciting again.

3. Mars is hard.

One of the most depressing images in planetary science history.

One of the most depressing images in planetary science history. Via www.link2universe.net

With the regular return of data and images from the rovers and orbiters currently working on and around Mars it can seem like success comes readily. However, like all space endeavours incredible successes on Mars are built on the foundation of repeated failures (rapid unplanned learning procedures). The Soviet Union was hot on the heels of NASA’s Mariner 9 and its Mars 3 probe made the first successful soft landing on Mars in 1971. That alone was an incredible achievement but the most exciting data would have been the first images from the surface. Unfortunately, after just 14.5 seconds of transmission, all communications ceased and all that was received was the image above, which reveals nothing of the martian surface.

4. Looking for Martians.

The surface of Mars.

The suitably beige surface of Mars in the 1970s. Via mojinos2006.blogspot.co.uk

The observations from Mariner 9 had massively excited Mars scientists and NASA’s next major mission to the planet would be a pair of orbiters and landers that would photograph the surface and land in regions that might host life. Before landing no one had any idea what to expect, some scientists thought that evidence of multi-cellular organisms might be visible in the photographs, but it was not to be. In the end the results of the life detection experiments were either negative or could likely be explained by non-biological chemical reactions. However, some of the results are still being debated to this day. The landers provided the first images from the Martian surface and scooped into soils to test their chemistry, as you can see from the trenches in the above photo. The Viking missions revealed an environment that was particularly unfriendly to life and the preservation of life molecules and enthusiasm for missions to the planet dimmed somewhat.

5. Learning to drive.

Sojourner rover roams around boulders delivered by an ancient flood.

Sojourner rover roams around boulders delivered by an ancient flood. Via imgkid.com

The modern search for life on Mars has shifted from looking for large living organisms in the present to microbial life that may have existed in the distant past. This has been prompted by observations from orbiting and surface missions that show Mars has experienced dramatic climate change from a likely warm and wet youth to the cold dry deserts of today. Life could also be possible on present day Mars but it would probably exist in a deep underground biosphere that would be hard to access. A significant part of that shift in understanding is due to the Pathfinder lander that arrived on Mars in 1997. The mission sent back chemical and photographic evidence that Mars had experienced floods and alteration by water in its past. It was also the first mission to deploy a rover, named as Sojourner, which demonstrated such technology could operate successfully on the planet. It also observed faint dust devils moving across the martian surface.

6. An alien sky.

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Sunset on Mars from Gusev Crater. Via nasa.gov

This is one of my favourite images from the surface of Mars, it shows a martian sunset in 2005, taken by Spirit rover. It looks like a shot from a Kubrick movie and while it feels like a somewhat Earth-like scene the significantly smaller appearance of the Sun is a reminder that this photo is from an alien world. While the daytime skies are an orange/brown twilight on Mars is blue. Images like this aren’t just pretty and thought provoking they also reveal how dusty the atmosphere of Mars is. Photos of the atmosphere can be useful for monitoring the progress of dust storms, which can be a significant hazard for missions. It was feared that missions using solar panels would have a short lifetime as dust coats the solar cells but it turns out the martian winds remove dust as well as adding it. This allowed Spirit and its sister rover Opportunity to have lifetimes well beyond their nominal missions.

7. Mars is still hard.

Spirit rover embedded in loose soil.

Spirit rover embedded in loose soil. Via nasa.gov

While Opportunity is still soldiering on Spirit rover is unfortunately no longer with us. In 2009 its wheels sank into soft soil from which the rover could not escape. Though it was the end of the mobile mission there was still some interesting science to be done. The soft soil was made up of a mineral known as iron sulfate, which likely formed in acidic wet conditions. This tells us more about the ancient environment of Mars and how benign neutral conditions gave way to more acidic and challenging habitats in Mars’ teenage years. On Earth acidic waters can still be home to life and it’s an intense area of study to see if minerals like iron sulfates might record evidence of ancient martian organisms. It’s also a good example of how Mars poses challenges not just to academics but also engineers. Testing rover twins on Mars like surfaces on Earth is a major part of planning before a mission as well as being used for addressing any problems that crop up when the actual rover is operating on Mars.

8. Mars is hard 3: Mars hard with a vengeance.

The Phoenix landing site in the northern polar regions of Mars.

The Phoenix landing site in the northern polar regions of Mars.Via jpl.nasa.gov

The Phoenix mission landed on Mars in 2008 and did a great deal of successful research into water on Mars and the kind of salts that might exist in potential martian brines. One of the salts it discovered was called perchlorate, which contains chlorine and oxygen. It is hazardous to human health, so it’s a potential concern for any future manned missions where dust might be an issue. However, it is also problematic for rovers on Mars as it breaks down easily and interferes with experiments used by Mars missions to look for life. Perchlorate has been detected by Curiosity rover so this problematic minerals seems to be widespread on Mars and mission experiments will have to be monitored for its influence.

9. Bolder and bolder.

Curiosity Rover as photographed by Mars Reconnaissance Orbiter.

Curiosity Rover as photographed by Mars Reconnaissance Orbiter. Via mars.nasa.gov

NASA has had enormous success sending missions to Mars and Curiosity Rover and the satellite Mars Reconnaissance Orbiter are the current peak of the agency’s efforts. Though orbiters do not grab headlines quite as often as surface missions they are just as important in attempting to understanding the planet. On the most basic level they allow the rovers to communicate with Earth. On a scientific level, while a rover gives an incredibly detailed view of a small area of Mars an orbiter can analyse information on a global scale. When an area becomes of interest a rover can be sent to establish ground truths and test the hypotheses of orbiter data. One issue is that often the most interesting areas are the most hazardous to land and will require either extremely advanced and robust rovers or the landing of people who can make the journey to all areas of scientific interest.

10. Where next?

Curiosity Rover being prepared.

Curiosity Rover being prepared. Via phys.org

One issue with photographs from the surface of Mars is that there is nothing to give us a sense of scale. I chose the image above as it show just how big Curiosity is and what an achievement it was to deliver such a large payload to another planet. As our understanding of the environment, history and hazards of Mars increases along with our ability to send ever more elaborate missions the question is what is our ultimate aim? There is the academic side of understanding the planet, which future rovers such as Exomars and Mars 2020 will seek to help with, but will we ever send people? It would be the most challenging expedition humanity has ever faced and right now I don’t feel there is the political or economic will to realistically drive that. Along with Mars science our knowledge of our own planet has improved significantly and we now recognise how fragile our biosphere is. Only time will tell if Mars will be the stepping stone for establishing a human presence beyond Earth.

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