Two new spacecraft join the Mars flotilla

The best view of Mars form Earth, taken with the Hubble Space Telescope. A growing number of spacecraft have been sent to study the Red Planet from close-up, including MAVEN and MOM ,which arrived this week. Image Credit: NASA/ESA and The Hubble Heritage Team STScI/AURA

On the 14th of July 1965, Mariner 4 became the first spacecraft to successfully flyby Mars, providing the first close-up images of the fourth planet from the Sun. Since then a host of spacecraft from several nations and space agencys  have flown past, orbited or even landed on Mars (along with many, many failures).

Growing interest in an eventual human mission to Mars has seen a surge in such missions over the past few years, most of them successful. Last week two new spacecraft joined the international flotilla of orbiters and rovers, including India's first interplanetary mission. So here, in order of arrival, are all of the active missions and what they're teaching us about Mars

Mars Odyssey

Artist's impression of Mars Odyssey, the oldest active spacecraft at Mars. Image Credit: NASA/JPL-Caltech

The first spacecraft to arrive at Mars in the twenty-first century was Mars Odyssey. Named after the book (and film) 2001: A Space Odyssey, this NASA orbiter reached Mars in, appropriately enough, 2001. Designed to study the chemistry of the Martian surface, its key discovery was the detection in 2002 of vast amounts of water ice lying just below the ground (click that link to be amazed by 12 year old internet...)

Whilst it has continued to make scientific observations, Odyssey has in more recent years fulfilled a vital role as a communications relay, transmitting information from the various landers and rovers on the surface to Earth and relaying commands back. I quite like this fact- we're beginning to build a space-based communications infrastructure at another planet!

Mars Express

Mars Express, the first European Mars orbiter. The long booms form the MARSIS sub-surface sounding radar, used to map the geology of the top few kilometres of the Martian crust. Image Credit: NASA  

Arriving in December 2003, Mars Express was the first European Space Agency mission to another planet. Based on the design of my current favourite mission, Rosetta, and sister craft to the near-identical Venus Express, Mars Express carries instruments to measure the chemical composition of the Martian atmosphere, surface and even subsurface. It also has a nifty spectroscopic camera allowing it to take high resolution, 3D images of Mars and, thanks to its unusually elliptical orbit, Mars' largest moon, Phobos.

In 2004 the spectrometers on Mars Express made an intriguing observation: signs of what could have been methane in the atmosphere. Methane should only last a few hundred years in an atmosphere before it reacts with the other chemicals around it, so for it to be present in detectable amounts means that something must be producing it. We know of several geological processes that could achieve this, but most methane production on Earth is biological. Could Mars Express have seen signs of life?

Mars Express also carried a lander, the British-built Beagle 2. Sadly however the landing was a failure, and contact was lost with Beagle 2 shortly after it entered the atmosphere on Christmas Day 2003. The reason for its loss is still unknown.

Opportunity

Panorama of Endurance Crater taken by the Opportunity Rover in 2004. One of the rover's solar panels can be seen in the bottom right (click to make bigger). Image Credit: NASA/JPL/Cornell 

The Mars Exploration Rover Opportunity is currently over ten years into a 90 day mission. Yep, you read that right.

January 2004 saw the arrival of two identical, six wheeled rovers on Mars. Following on from the highly successful Pathfinder mission, Spirit and Opportunity parachuted through the thin atmosphere and landed via an innovative airbag system. Original planned to last just three months and drive around a kilometre across the surface, both rovers far exceeded their targets. Spirit became stuck in sand in 2009 and didn't survive the winter (the xkcd on the topic is essential reading), but Opportunity is still going strong, having covered a distance of over 40 kilometres.

The full list of discoveries made by this stupendously successful mission would be several posts on its own, so in the interests of word count I'll talk about just one. Early in its mission Opportunity was sent to investigate the wreckage of the heat shield that had protected it during its entry into the Martian atmosphere. Near the heat shield was a strange, dark-coloured rock, out of place with the geology around it. Opportunity had discovered the first meteorite on anther planet.

The meteorite, dubbed Heat Shield Rock, was a lump of iron and nickel leas than half a metre across. Its existence was a mystery: Mars' thin atmosphere couldn't have slowed it down enough to stop it vaporising when it hit the ground. So perhaps at some point in the past Mars had a much thicker atmosphere, an atmosphere that it has since lost?

Mars Reconnaissance Orbiter
   

Over 250km above the Martian surface, the Mars Reconnaissance Orbiter easily spots the 1.6 metre long Opportunity. Image Credit: NASA

Since the before the start of the Space Age, landing people on Mars been high up the wish-list of things to do in space. A key requirement for that, as well as for larger robotic landers, is high-resolution mapping of the Martian surface. In 2006 the Mars Reconnaissance Orbiter (MRO) arrived to do just that.

Significantly larger than its predecessors, MRO's main instrument is 0.5 metre downwards-pointing telescope. The High Resolution Imaging Science Experiment, or HiRISE, is the largest telescope ever sent to another planet and can image the Martian surface at resolutions down almost 30sm/pixel.

HiRISE, together with several other instruments, has allowed us to explore huge swaths of the Martian surface in great detail. Among its many achievements has been providing evidence for brief flows of running water, as well as spotting parachuting landers heading down to the surface.

Curiosity 

The largest lander ever sent to another planet, the Mars Science Laboratory Curiosity landed via a highly complex skycrane system in 2012. Here, the nuclear-powered rover takes a selfie, next to a rock that it has drilled into  (middle left) to obtain a sample for it's onboard laboratory. Image Credit: NASA 

A common complaint about a perceived lack of technological progress is "where's my jetpack?" Whilst a person using a jetpack would actually be a really silly idea, that question does now have an answer. It's on a nuclear powered, laser equipped mobile science lab on Mars.

At 900kg, the Mars Science Laboratory, better known as Curiosity, was far too large for it to land using air bags like Spirit and Opportunity. Instead they used a skycrane, a rocket powered aircraft that slowed the rover down from 200 mph to zero before lowering it down on cables. This video has the full details of an operation that surely ranks among  the most difficult and technologically impressive achievements of humankind.

Curiosity's primary mission on Mars was to determine if the conditions on Mars could at some point in its past have been suitable for life. By the end of its first (Earth) year on the Red Planet Curiosity had met its scientific objectives, showing that the rocks around it had once formed part of a lake bed, with water and all of the chemical ingredients needed for life.

The Mars of several billion years ago was evidently very different to the barren planet we see today. However, Curiosity found no trace of the methane in the atmosphere that had been detected years earlier by Mars Express.      

Completing its primary mission in August, it has not all been smooth driving for Curiosity. NASA's recent Senior Review of its planetary exploration missions found that the rover was not being used to its full scientific potential, and that a better balance between  driving and taking data needs to be found. Whatever its troubles, Curiosity will certainly make more exciting discoveries over the next few years, as it begins to climb a 6km high mountain.

MAVEN

Arriving at Mars last week, MAVEN has been sent to find out what happened to Mars' atmosphere. Image Credit: NASA

Finally we come to last week's new arrivals. First to arrive was the  Mars Atmosphere and Volatile Evolution (MAVEN), a NASA mission. As a wide range of general scientific capabilities is already present at Mars, MAVEN's mission is somewhat more specialized than previous spacecraft. Its primary objective is to find out what happened to Mars atmosphere.

To support, for example, the prehistoric running water and intact meteorites found by previous missions, Mars must have had a thick atmosphere similar to the Earth's. Yet all that remains now is thin shell of carbon dioxide. Where did the atmosphere go?

In an attempt to answer these questions MAVEN will be sent on a daring mission into the upper reaches of Mars' atmosphere. The bent shape of its solar panels, seen in the artists impression above, will help with this, allowing it to remain stable as it becomes in effect our first interplanetary aircraft.

There, its advanced suite of spectrometers along with a magnetometer, will measure in detail the composition of the atmosphere and, crucially, its interaction with the solar wind. As Mars has no global magnetic field to protect it, the force of the solar wind has become the prime suspect in the case of the missing atmosphere.

MOM

MOM is the only Mars orbiter capable of taking images of the whole of Mars in one go. Compare with the HST image at the start! Image Credit: ISRO

Arriving into Martian orbit on Friday 24th September, The Indian Space Research Organisation's Mars Orbiter Mission (MOM) has one notable difference with all the spacecraft to have come before it: The price tag.

Although the quote value of $74 million probably doesn't take all of its costs into account, MOM still cost many times less than MAVEN. Despite this, it has a small yet advanced suite of instruments, These include the first camera capable of taking full-disc images of Mars, as well as a dedicated methane detector which will try and finally nail down the story of this elusive gas in Mars' atmosphere. Although MOM only has a six-month mission planned, plans made this week to share science data with NASA suggest that it many well keep going for some time.

India's success in pacing a spacecraft into Martin orbit may be the start of a new stage in space exploration, showing that exploring the solar system isn't limited to a few select countries and can be done without spending billions. India, and the countries that follow it, will reap the technological benefits from these missions just as the "traditional" spacefarers have done before.

And that's it! With seven working spacecraft now on or orbiting Mars, as well as more missions launching soon, we are learning more about the fourth planet from the Sun than ever before. Within our lifetimes we may finally find out whether Mars once supported life, or even if it has any now. And the more we study the Red Planet and how to get there, the closer humankind gets to finally voyaging from Earth to join our robotic explorers.

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