The discovery of the Beagle 2 lander, hailed by planetary scientists, solves a decade-old mystery as to the fate of this missing spacecraft -- and may reveal what exactly led to its untimely demise.
Mark Sims of the University of Leicester, who served as the spacecraft’s mission manager, expressed "elation that we’ve found it."
The U.K.-led Beagle 2 hitched a ride to the Red Planet with the European Space Agency’s Mars Express spacecraft, with the goal of searching for signs of life on Mars, past or present.
This was an ambitious endeavor. By comparison, NASA’s twin rovers Spirit and Opportunity, which reached Mars just weeks after Beagle 2, were sent with a much simpler goal: to look for signs of water. Even the high-tech 2012 rover Curiosity went with a more modest goal: to find hints of habitable environments.
On Christmas Day 2003, around 2:51 a.m. in England, Beagle 2 entered the Martian atmosphere – and was never heard from again. The scientists waited for a signal from the spacecraft, but none came. In February 2004, the lander was officially declared lost.
Other spacecraft scoured Beagle 2’s landing area in Isidis Planitia, an impact basin close to the equator, with no luck.
“It really is a needle-in-a-haystack job,” Sims said.
A few possible sightings were reported in the years since. But the Beagle 2 was small -- around 73 pounds, compared to the Curiosity rover’s 1-ton weight -- and hard to pick out on the surface. None of the orbiters seemed to have a powerful enough camera to conduct the search, until the Mars Reconnaissance Orbiter arrived in 2006.
The orbiter’s HiRISE camera, with its roughly 30-centimeter-per-pixel scale, was roughly 10 times better than its peers. It has pinpointed the location of a host of other Martian spacecraft, and for good scientific and engineering reasons, said Richard Zurek, project scientist for the Mars Reconnaissance Orbiter at the Jet Propulsion Laboratory.
“These are known objects to us, and we can look at how they’re changed by being in the Mars environment,” said Zurek, who was previously project scientist for another long-missing (and still-lost) spacecraft, NASA’s 1998 Mars Polar Lander.
The spacecraft began to image the landing site in bits and pieces as it circled the planet, but there were few leads until Michael Croon of Trier, Germany, who was once part of the Mars Express operations team, started looking through the HiRISE images himself. Croon spotted a strange little feature on the surface that did not look like a Martian rock, and sent the information along to his former colleagues. The scientists followed up with more images, including one in color.
Having multiple images was key, Zurek said -- with only one, the scientists wouldn’t be able to say for sure whether it was real, or a flaw caused by a cosmic ray hitting the camera.
“When you get multiple [images], particularly from different viewing angles, you begin to get an idea of the shape of this object," Zurek said, "which is really at the limit of your resolution otherwise.”
Two objects near the spacecraft matched where the parachute and rear cover would have landed. The evidence all lined up, Sims said.
“You see something which isn’t red, you see something which doesn’t look like a rock, you see something which is very flat because it doesn’t cast a shadow,” Sims said. “It’s not a blob, it’s actually got structure to it, and that structure is consistent with the shape of Beagle 2 and the size of Beagle 2. It’s in the right place, it’s in the landing-site ellipse, just in the 5 kilometers from the center of that ellipse.”
Alfred McEwen, lead scientist for HiRISE at the University of Arizona, agreed.
“I feel like we should have found it sooner, in fact,” McEwen said with a laugh. “It was very close to the predicted landing site.”
It appears that at most, only two or three of the spacecraft’s solar panels deployed, Sims said. This was a fatal problem for the lander, given that the radio antenna was packed underneath the solar panels, and would remain blocked until all four solar petals had unfolded into their flower-like pattern.
Without the radio antenna, there was no way to reach the lander.
It’s possible the hardware might have been damaged during a hard bounce as the spacecraft hit the Martian surface, Sims said -- perhaps an ill-placed rock punctured the airbag landing system.
The fact that the spacecraft at least partially deployed means that the entry, descent and landing process succeeded – which is good news for engineers designing future missions, McEwen said.
Nonetheless, Sims said, it was also frustrating to see how close the lander came to actually starting its science mission.
“We came so close,” said Sims, who also expressed sadness that the scientist who spearheaded the mission, Colin Pillinger of Open University, died in May last year and did not live to witness the rediscovery.
Still, the Beagle 2’s discovery was an opportunity for some resolution, said Zurek, who said he still held out hope that his own previous mission, the 1998 Mars Polar Lander, might one day be discovered.
“Since I was the project scientist for a missing spacecraft ... I can certainly appreciate the sense of closure that knowing that this thing actually made it safely to the surface of Mars would give the Beagle 2 team,” Zurek said.
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