High resolution image of Mars rover Curiosity as taken by the rover's robotic arm-mounted camera.NASA/JPL-Caltech
On Aug. 5, 2012, at 10:31 p.m. PDT, I was standing in silence (with Discovery News' Irene Klotz and Amy Teitel) in the NASA Jet Propulsion Laboratory's press room with dozens of representatives from national and international media. We were all transfixed on one large TV screen that showed views from JPL mission control (a mere stone's throw from the media gathering) and flashed up computer renderings of the descending rover approaching the Martian surface.
As soon as the signal was received from Mars that the mission had successfully touched down inside Gale Crater, the TV depicted scenes of pure jubilation and the press room erupted first with cheers, then rapid mouseclicking as all the major news outlets released the good news to the world. The celebrations were quickly followed by the first photographs through Curiosity's eyes, marking the beginning of the mission that, very quickly, would transform our knowledge of the red planet.
So, just one year on from the exciting entry, descent and landing (EDL) -- a.k.a. "The Seven Minutes of Terror" -- let's review some of the key discoveries that Curiosity has made so far in its epic adventure on Mars.
A selection from the panorama of Gale Crater as taken by Curiosity on Aug. 8, 2012.NASA/JPL-Caltech
As soon as Curiosity opened its camera lenses and started to image this never before seen region of Mars, the first thing that struck JPL scientists and the public alike was the instant familiarity we had with the landscape.
"The first impression you get is how Earth-like this seems," lead scientist John Grotzinger told reporters on Aug. 8, 2012 -- three days after landing. "You would really be forgiven for thinking that NASA was trying to pull a fast one on you and we actually put a rover out in the Mojave Desert and took a picture, a little LA smog coming in there."
He was referring to the haze seen in this photograph that was slightly obscuring the distant rim of Gale Crater. In the past year, the Martian atmosphere has shown itself to be highly variable, often obscuring the rover's view of its ultimate goal, Mount Sharp.
The Jake Matijevic rock, one of the rover Curiosity’s first targets of study, has a history that more closely resembles some rocks on Earth than previously studied rocks on Mars.NASA/JPL-Caltech
In the weeks that followed Curiosity's touchdown at Bradbury Landing, Curiosity tried out its sophisticated suite of instrumentation. One instrument, ChemCam (the boxy "head" of Curiosity), fired its laser at a target rock dubbed "Jake Matijevic."
After analyzing the results, mission scientists confirmed that not only was the rock formed through volcanic processes, it had astonishingly similar characteristics as igneous rocks found here on Earth. Interestingly, the minerals in these types of rock form from a similar process to what colonists used to make booze from apple cider.
The first analysis of X-ray diffraction on Martian soil by the Chemistry and Mineralogy (CheMin) experiment. The soil sample, taken from a wind-blown deposit within Gale Crater, where the rover landed, is similar to volcanic soils in Hawaii.NASA/JPL-Caltech
The resemblance of the Martian landscape to deserts on Earth was quickly apparent; even the volcanic rock seems to have formed in the same way that they do on Earth. In the following November, Curiosity scientists had another groundbreaking discovery for the world.
After collecting regolith samples from a sandy rift in a geologically interesting area called “Rocknest,” Curiosity's Chemistry and Mineralogy (CheMin) instrument was used to analyze a scoop of the stuff. Through X-ray diffraction analysis -- the first time the technique has been done on another planet -- the Martian soil was found to contain similar volcanic minerals as a very specific place on Earth: Hawaii.
A photograph of an area near Curiosity at Bradbury Landing showing layered deposits of conglomerate material, a strong indication that a river used to flow here.NASA/JPL-Caltech
Curiosity's prime mission is to seek out evidence of habitability, past or present, on the Martian surface. A key criteria of "habitability" is water. Did liquid water used to flow over the Martian surface in abundance? As this jaw-dropping discovery shows, the answer is a very positive yes.
Near the rover's landing site, Curiosity snapped images of small rounded pebbles. Pebbles? Yes, pebbles on Mars.
On Earth, pebbles are formed when rocks undergo erosion by fluvial (water) action. The presence of pebbles and large slabs of sedimentary rock packed full of pebbles of different sizes -- known as conglomerates -- is evidence that Curiosity's landing site used to be a riverbed. This discovery strengthens the possibility that, if there used to be large quantities of liquid water on Mars, ancient microbial life may have been able to gain a foothold.
This image of an outcrop at the “Sheepbed” locality, taken by NASA’s Curiosity Mars rover with its right Mast Camera (Mastcam), shows show well-defined veins filled with whitish minerals, interpreted as calcium sulfate.NASA/JPL-Caltech
It's one thing to discover pebbles at a certain location, but when you find evidence of minerals that could have only been formed in the presence of water, you begin to get a sense that that place used to be pretty darned wet. Of course, this place is Mars, currently one of the most barren places in the solar system... but it wasn't always this way.
While imaging a rock known as "John Klein," mission scientists noticed white veins of a mineral passing through the rock. After drilling actives and dust samples analyzed, its nature was confirmed. Calcium sulphate -- a.k.a. gypsum -- was found. The presence of the mineral, also discovered on the other side of the planet by NASA's veteran Mars rover Opportunity, is further evidence that Mars used to have large quantities of water on its surface.
Mars' atmosphere from orbit.NASA
Mysteriously, Curiosity can't seem to find any trace of methane in the air -- a factor that contradicts orbital data that suggests otherwise. This is one mystery that will have to go on hold for the time being. But the mystery of Mars' thin atmosphere is slowly being solved.
With the help of Curiosity's measurements of the Martian air, isotope analysis suggests that Mars actually had a very thick atmosphere some 4 billion years ago. Without the protection of a global magnetic field, however, the planet wasn't able to retain its atmospheric gases from the ravages of the solar wind that stripped it into space. This is one factor that likely impacted the red planet's habitability.
Mars' moon Phobos eclipses the sun from Curiosity's vantage point.NASA/JPL-Caltech
Designed as the most sophisticated mechanized geologist for tens of millions of miles, Curiosity also moonlights as an astronomer. The rover has had many opportunities of watching the sun rise and set. It has also seen Mars' moons Phobos and Deimos fly overhead. And sometimes, Curiosity has the rare opportunity to spot an extraterrestrial eclipse. Shown here, Mars' largest moon partially eclipses the sun on Sept. 13, a month after landing.
Artist's impression of humans on Mars.Pat Rawlings/NASA
To every Mars coin, there's a flip side. While the discovery of gypsum may be evidence of water action in Mars history that, in turn, suggests there may have been enough liquid water to support basic biology, gypsum is known to be toxic if breathed in by humans. Also, Curiosity has confirmed the presence of another rather nasty chemical, perchlorates. Although perchlorates are used by some hardy microbes on Earth as an energy source, the chemical is a rocket fuel oxidizer known to poison people.
Add that to the radiation risks, and the fact that Mars dust will likely be hard to clean from spacesuits, and Mars is looking like a very precarious place for humans to explore. But any exploration of an alien world would be dangerous, so our future Mars explorers will likely chalk these scary factors up to the risks of doing bold things in space.
Curiosity looks down at its filled scoop... plus a mystery object on the ground.NASA/JPL-Caltech
This isn't a Curiosity discovery per se; it's more of a study into the human fascination with Mars and how NASA's rover has facilitated that interest.
Scouring over the gigabytes of data streaming from Curiosity, eagle-eyed armchair space explorers have spotted some strange things in the pictures snapped by NASA's mission. First up, when scooping samples of Mars dirt in October, a shiny object was spotted by Curiosity's wheels. Sadly, it wasn't proof of an alien snakeskin, it was in fact a piece of plastic from the rover itself. Add that to the growing list of Mars rats and random Mars flowers and we quickly realize that the phenomenon of pareidolia is alive and well.
But this also proves that we just can't keep our eyes off this incredible mission to Mars.