One year on, one kilometre travelled, a mission goal achieved

CuriosityOn the 5th/6th August 2012, an aerodynamic capsule large enough to hold compact family car separated from its cruise stage “life support” system after an eight-month journey from Earth and blazed a trail across the high, thin atmosphere of Mars at the start of what those responsible for it had dubbed the “seven minutes of terror”.

Inside that aeroshell was the most advanced remote science system yet sent into interplanetary space by humankind, 80 kg (around 180 pounds) of science equipment packaged neatly into a rover vehicle itself just under a tonne in weight and powered by a “nuclear battery”. If all went well, those “seven minutes of terror” would end with NASA’s latest and most ambitious mission to the planet Mars safely on the surface of that world. If things went badly, a lot of people would be looking at almost a decade of their endeavours smashed to pieces along with the rover.

The Mars Science laboratory spacecraft systems: (1) Cruise Stage; (2) aeroshell back shell; (3) Skycrane; (4) Curiosity rover; (5) Heat shield; (6) Parachute system

Of course, things did go well. The rover, dubbed “Curiosity” by an 11-year-old girl called Clara Ma following a nationwide competition held by NASA in 2008, landed safely and so wrote the first lines in what have been a remarkable year of operations on Mars.

Just over half-way through its primary phase of a full Martian year (about 1.8 times longer than a year here on Earth), Curiosity and the Mars Science Laboratory mission has already achieved a major part of its mission goal: to discover if Mars demonstrates any evidence for once having the kind of environment conducive to the formation of life.

And with the mission indefinitely extended beyond that primary mission phase (the rover’s RTG power system should be able to power it for around 14 years or so, so only the unforeseen accident or failure might now curtail the mission in less than that time frame), the opportunities for Curiosity to write many more new chapters in our understanding of Mars are considerable.

Over the last year, as an aside to my reporting on Second Life and virtual worlds (as well as one or two other things!), I’ve tried to provide a steady narrative on the mission in these pages (with more than a little help from NASA JPL!), I’ve done so as space exploration is of interest to me for assorted reasons, and because the reports seem to have resonated with some of you who regular read this blog (and thank you on both counts, for  reading the blog and the reports!).

Obviously, as with all things fresh and exciting, coverage of the mission in the early months was easy; such was the media interest in the story that information was flooding out of NASA’s Jet Propulsion Laboratory as the rover went through its month-long post-landing commissioning activities, and then started its first hesitant operations on the dusty, wind-swept floor of Gale Crater.

With the passing of a year, media interest has moved on. As a result, the science and engineering teams responsible for the mission have been able to focus more on their day-to-day work, and the updates coming out of NASA have slowed somewhat.

Curiosity is now well into the eight kilometre (five miles) drive to its next target: the lower slopes of Aeolis Mons (“Mount Sharp”), the mound surrounding the central peak of the crater. In the six weeks since departing “Glenelg” and “Yellowknife Bay”, where it had been engaged in science activities for almost six months, the rover has travelled almost a full kilometre.

Traversing Mars: from the arrival point of “Bradbury Landing” to Curiosity’s position on Sol 365 (August 16th, 2013) this map traces a remarkable journey (click to enlarge)

That the rover is making “rapid” progress is down to two things: there are no planned science objectives for this phase of the mission (unless Curiosity happens across something completely unexpected and interesting), and the rover’s drive team have gained considerable confidence in the upgraded autonomous driving capability I reported on last time around.

Curiosity’s primary mission is not to find direct evidence of life, past or present, on Mars, but rather to see if ancient Mars once had the right conditions present in or on it for life to have possibly arisen. Gale Crater was chosen as a landing site with this in mind; since well before the mission it has been the subject of study from orbit by the likes of NASA’s Mars Odyssey and Mars Reconnaissance Orbiter and Europe’s Mars Express. That it has surface features which appear consistent with free-flowing water once having existed on Mars have been well-known, including the fact that “Mount Sharp” itself shows signs of having been in part formed from water-borne sedimentary deposits (it is thought Gale Crater may have once been filled with a lake). As such, it was anticipated that the rover would find evidence of free-flowing water having once been present within the 194-kilometre wide crater.

What wasn’t expected was the overwhelming evidence the rover came across in terms not only of sedimentary deposits, but also in what look to be ancient river beds sitting exposed on the floor of the crater, and rock and soil samples the on-board science systems have found to contain mineral and chemical elements and traces which point to a wet history in this part of Mars. What has been more exciting is that the mix of elements and minerals suggest the environment in the crater was once very benign towards life, so much so, that John Grotzinger, the mission’s Principal Investigator, was given to comment:

We have found a habitable environment that is so benign and supportive of life that probably, if this water was around and you had been there, you would have been able to drink it. We have characterized a very ancient, but strangely new ‘grey Mars’ where conditions once were favourable for life.

Of course, finding evidence of what might have once been a potential habitable environment and finding evidence that life did in fact come into being within that environment are two vastly different things, and we’ll have to wait for something like NASA’s Mars 2020 mission or Europe’s ExoMars before we get nearer to answering whether or not Mars was once the abode of life, however primitive.  Nevertheless, that Curiosity has fulfilled an initial science goal so early into the mission and with such remarkable success can only bode well for the future.

Destination Aeolis Mons: Two versions of a "deep zoom" shot of the mount captured on Sol 45 (Sept 20th, 2012). The upper image is as the scene appears under normal Martian daylight conditions, the lower has been "white balanced" to show the scene under normal Earth daylight conditions
Destination Aeolis Mons: Two versions of a “deep zoom” shot of the mound captured on Sol 45 (Sept 20th, 2012). The upper image is as the scene appears under normal Martian daylight conditions, the lower has been “white balanced” to show it under normal Earth daylight conditions (click to enlarge)

Over the last year Curiosity has returned a huge amount of data, almost 24 gigabytes, which includes over 70,000 images, of which just over half are medium or high-resolution shots, the rest thumbnails.  The ChemCam laser mounted at the top of the rover’s mast has been fired more than 75,000 times at 2,000 targets, providing a fair portion of the data returned to Earth, alongside the findings from the rest of the science instruments, including the on-board Chemical and Mineralogy systems and the Sample Analysis at Mars systems, which are the rover’s scientific heart and soul.

To mark Curiosity’s first anniversary of its time on Mars, NASA released a special video allowing people to relive the entire mission to date in two minutes.

Astronomical Observations

Nor has Curiosity been confined to ground-based studies or monitoring the dynamic environment of the Martian atmosphere. Several times during the mission the cameras on board have been used to make astronomical observations, particularly of Mars’ two moons, Phobos and Deimos.

The most recent of these events occurred on August 1st 2013, when Curiosity was ordered to turn its Mastcam system to the night sky and use the telephoto lens to capture a series of images as Phobos, the nearer of the two moons relative to the surface of Mars, passed in front of Deimos as seen from the rover’s position.

To mark the event, NASA released an image comparing the apparent sizes of the Martian moons when seen from the surface of Mars, in relation to Earth’s Moon when seen from the surface of the Earth.

Left: Phobos (foreground) passing in front of Deimos as seen by Curiosity on August 1st, 2013. Both moons have been oriented in the image so north is at the top. Right: a comparative image of Earth’s Moon as seen from Earth, again oriented with north at the top. The “large” size of Phobos and Deimos is purely down to the fact they orbit much closer to their “parent” planet (click to enlarge)

The composite image is somewhat deceptive, as the Moon is over 100 times greater in size than Phobos, but both Phobos and Deimos are much nearer to their “parent” planet. The Moon, with a diameter of some 3,474 km (2,159 miles) averages about 380,000 km (238,000 miles) from an observer on Earth. By comparison, Phobos has a diameter of roughly 22 km (14 miles), and was some 6,240 km (3,900 miles) from Curiosity when the images were captured, while Deimos is just 12 km (7.5 miles) across and was around 20,500 km (12,800 miles) from the rover.

The images captured by Curiosity were put together to make a short film of the event. However, the purpose in capturing the Martian moons in this way isn’t just to mark and event or make movies. Observing Phobos in particular allows scientists to improve their understanding of the little moon’s orbit, allowing them to better understand what, and how much, tidal influence Phobos exerts on the interior of Mars (just as the Moon exerts a tidal influence not only on the oceans of Earth, but also on the interior of the planet as well).

Both Phobos and Deimos are most likely to be asteroids, although whether they once orbited the Sun freely before being trapped by Mars’ gravity or whether they are the last survivors of many small asteroidal bodies which once orbited Mars as a result of a collision with a large planetesimal in the early history of the solar system, is still the subject of debate. As it is, both moons are tidally locked with Mars, always presenting the same face towards the planet.

As Phobos is orbiting Mars faster than the planet rotates, it is effectively slowly “falling” toward Mars as a result of tidal forces. Eventually it will reach what is called the Roche limit, and break-up, the remnants bombarding Mars in a manner akin to that of the Shoemaker-Levy 9 collision with Jupiter in May 1994. When this happens, it will result in a line of new craters being formed on Mars, and the presence of such crater “strings” on the surface already is seen as evidence that Phobos and Deimos were, along with many now “deceased” moonlets, the result of the ancient collision mentioned above.

By contrast, Deimos, being much further from Mars and orbiting it more slowly than the planet’s rotation (it takes around 30 hours to complete an orbit), is slowly slipping free of Mars’ grasp and will one day escape.

But that’s a long time in the future. For now, I’ll come back to the present and leave you with one of the great photos released on the 5th/6th August 2012, as the Entry, Descent and Landing team at JPL received telemetry from Mars confirming Curiosity had landed safely, some 16 minutes after the rover had in fact arrived, the delay caused by the time signals take to pass between the two worlds.

Adam Steltzner (right), the man who lead the team responsible for the Curiosity's descent and landing systems, responds to news that Curiosity has arrived on Mars (credit: Brian van der Brug/Los Angeles Times-POOL)
Adam Steltzner (right), the man who lead the team responsible for the Curiosity’s descent and landing systems, responds to news that Curiosity has arrived on Mars (credit: Brian van der Brug/Los Angeles Times-POOL)

MSL reports in this blog

All images courtesy of NASA / JPL unless otherwise credited