Landing on Mars is hard, but the European Space Agency's first attempt -- the Beagle 2 probe -- came maddeningly close to being a complete success. In fact, a new 3D modelling analysis shows that the lander's failure to communicate with the Earth was likely due to a single jammed solar panel.
Artist's impression of the British Beagle 2 lander, its four solar panels properly deployed, collecting data on the Red Planet's surface. Image: ESA/Denman productions
A British space probe designed to hunt for signs of life on Mars, Beagle 2 was launched aboard ESA's Mars Express spacecraft in June 2003. It was released from its mothership on December 19 and scheduled to land on the Red Planet six days later. But Beagle 2's Christmas day phone call home from Mars never came -- and subsequent searchers by Mars Express and NASA's Mars Odyssey were unable to locate the lander.
For more than a decade, its fate remained a mystery.
An interpretation of one image of Beagle 2 captured by HiRISE. Image: Tim Parker/JPL/NASA/University of Leicester
In late 2014, after nearly everyone had given up on the lost lander, Beagle 2 was spotted in a series of eight images taken by the HiRISE camera on NASA's Mars Reconnaissance Orbiter. The blurry, pixelated photos showed what appeared to be an intact lander, along with its parachute and heat shield nearby. But even after applying advanced image processing techniques, scientists were unable determine the configuration of the lander -- the photos were simply too low resolution. The question of what the hell went wrong remained open.
But Mark Sims, a professor of astrobiology at the University of Leicester and former mission manager for Beagle 2, wasn't about to let the mystery go, not after obtaining photographic evidence of a successful landing. "Call it stubbornness, if you like," he told Gizmodo. "In the end, all of this is about trying to figure out exactly what happened to Beagle 2."
An idea came to Sims one evening last autumn in the US, toward sunset, after tracing the source of a bright glimmer in his lounge to the reflection of a window down the road. "I looked at that light and thought, 'There's information here about what I'm seeing,'" he said. Specifically, Sims started thinking about how the appearance of an object can change drastically with the angle of the Sun.
Gif showing sequence of images taken by the Mars Reconnaissance Orbiter's HiRISE camera at different sun angles.
The HiRISE images of Beagle 2 were all taken at different Sun angles, and in each of them, the lander reflects light in a slightly different way. And so, Sims started to wonder: If the Beagle 2 lander could be simulated under different lighting conditions, could one work out its configuration on the surface?
"It's an old idea, in a sense," Sims said. "But I didn't have the knowledge or technology to do the analysis."
As luck would have it, a friend of Sims' introduced him to someone who did: Nick Higgett, a researcher at De Montfort University whose lab uses advanced 3D modelling techniques to reconstruct historic sites around Leicester.
Taking Sim's "reflection analysis" concept, Higget and his team constructed a 3D model of the Beagle 2 lander, which is shaped like a clam shell and opens in half before unfurling four solar panels on one side. They modelled the lander in several different configurations, with one, two, three or all four solar panels deployed. The model was then scaled down to the pixel resolution of the Mars Reconnaissance Orbiter's images, and bathed in virtual sunlight at different angles. Finally, its reflection patterns were compared with real images of Beagle 2 captured by Hi-RISE.
Satellite images from HiRISE and simulated Beagle 2 images, at high resolution and scaled down. Image: De Montfort University
"We looked at a lot of different configurations in our simulations and saw which was most consistent across a number of [Hi-RISE] images," Higget told Gizmodo. "There was a lot of trial and error."
Eventually, the researchers determined that the best match between real and simulated reflection patterns was one in which Beagle 2 had three of its four solar panels deployed, although a four panel scenario was also possible.
Entry, descent and landing sequence for Beagle 2. Image: Beagle 2
"This confirms that the Beagle 2's entry, descent and landing system worked," said Sims, who is currently writing up the findings for publication. "It got down to the surface, and it was intact. Furthermore, it was within one solar panel of being fully deployed and fully operational."
All four of the Beagle 2's solar panels need to open before an RF communication antenna could pop out and send signals back to Earth. So, if the the three-panel scenario is correct, that explains why we never heard from the lander. If all four of the panels did deploy, there must have been some other technical problem. It could have been as minor as a bad electrical wire or a loose screw.
"I suspect, given what we've seen from prior data analysis back in 2015, it's the three-panel scenario," Sims said. "But if all four panels did open, we were excruciatingly close to having a working spacecraft on the surface of Mars."
We may never be sure exactly what went wrong with Beagle 2, although Sims is keen to do more simulations if he receives the funding. Higget notes that his team's newly devised technique could be applicable to other situations where scientists are trying to understand a highly-reflective object on the surface of a different planet or even in a remote area on Earth.
Unfortunately, reflection analysis won't be applicable to the European Space Agency's recently-crashed Schiaparelli lander, which impacted the surface at a very high speed and seemed to explode, leaving nothing but a dark burn mark. "That was a great disaster for the team, and I feel deeply for them," Sims said. "But it was obviously a crash."
Beagle 2, meanwhile, obviously wasn't a crash. And while it may seem a bit arcane to continue puzzling over the pixelated reflections of a machine that died on Mars more than a decade ago, who knows? Maybe in those glimmers, we'll learn something that will keep the next space probe alive.