An Indian spacecraft’s unprecedented attempt to make a soft, controlled landing in the moon’s south polar region has ended in excruciating silence: Shortly before touchdown, the robotic lander Vikram—part of the Chandrayaan-2 mission—fell out of contact with mission control. The Indian Space Research Organization, India’s space agency, says that the spacecraft stopped communicating with Earth when it was within two kilometres of the lunar surface.
“The Vikram descent was as planned, and normal performance was observed, up to an altitude of 2.1 kilometres,” said Kailasavadivoo Sivan, ISRO’s chairman, in a statement roughly half an hour after signal loss. “The data is being analysed.”
In addition to setting a global first, a successful landing would have made India just the fourth country to touch down anywhere on the lunar surface, and only the third nation to operate a robotic rover there. Nevertheless, the Chandrayaan-2 mission’s orbiter remains safely in lunar orbit, with a year-long scientific mission ahead of it.
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“India is proud of our scientists! They’ve given their best and have always made India proud,” Indian prime minister Narendra Modi said in a statement on Twitter after Sivan’s update. “These are moments to be courageous, and courageous we will be!”
Like any voyage to a world beyond Earth, Vikram’s flight was a risky endeavour, requiring the lander to slow itself down to a near standstill, autonomously scan for surface obstacles, and then take steps to avoid them during touchdown. The majority of attempts to land robots on the moon have ended in failure, either during launch or on the way to the surface.
“Even though we got a successful lunar orbital insertion, landing is the terrifying moment,” Sivan said in an August press conference.
In an interview before the attempt, Dana Hurley, a planetary scientist at Johns Hopkins University’s Applied Physics Laboratory, expressed the nervousness that planetary scientists around the world feel with every spacecraft landing—because they know all too well what can go wrong.
“We’re always excited and nervous, because we know it’s very hard to do,” Hurley said. “It’s a tough business.”
Following its launch on July 22, Chandrayaan-2 spent the last several weeks inching its way to the moon, ultimately entering lunar orbit on August 20. On September 2, Vikram separated from the mission’s orbiter, and the newly freed lander began a series of braking manoeuvres to lower its orbit and ready itself for landing.
Had things proceeded without a hitch, Vikram and Pragyaan—the small solar-powered rover it carried—would have set down on the moon at a latitude of about 70 degrees South, on a highland between the craters Manzinus C and Simpelius N.
While not technically at the lunar south pole, Chandrayaan-2’s target site was by far the southernmost ever selected for a soft lunar landing. The next southernmost lander, China’s Chang’e-4, sits at a southern latitude of about 45.5 degrees on the moon’s far side, about 1,931 kilometres from Vikram’s targeted site.
This landing site was “somewhere new that we haven’t seen before, so that makes it another area for ground-truthing remote sensing data,” Clive Neal, a lunar geologist at the University of Notre Dame, said in an interview before the landing attempt. “It [was] going to certainly enhance our knowledge of what the moon is like in those areas, so it [was] going to be another very good place for science and exploration.”
Chandrayaan-2’s scientific goal is to study the south polar region’s distribution of water ice and other so-called volatile compounds. The orbiter component will still be able to make high-resolution maps of the lunar surface, as well as the occurrence of certain elements such as magnesium. Its radar system will also be able to “listen” for the telltale ping of water ice mixed into lunar soil.
“The orbiter instrument suite itself would widen the horizon of information, with extended coverage in the infrared range to more accurately capture [the] hydration character of the lunar surface,” Deepak Dhingra, a planetary scientist at the Indian Institute of Technology, Kanpur, said in an email after the landing attempt. “There is an enormous amount of science waiting to happen! Stay tuned.”
But scientists around the world were awaiting results from Vikram and Pragyaan most of all. Previous lunar missions, including India’s Chandrayaan-1 orbiter, found evidence that soils at the lunar poles contain water ice, which could be an invaluable resource to future lunar astronauts. Lunar ice also archives the history of the early solar system, since water arrived at the moon in one of several ways, including ancient comet impacts.
“The entire globe is waiting for our data,” Sivan said in August. “This will be giving input for a future program [that] is concerning humanity in a major way.”
All eyes upward
However, landing at such a high latitude is no small feat. During the crewed Apollo missions, NASA designers didn’t attempt any landings near the lunar poles out of safety concerns. If the Apollo spacecraft’s rocket engine had failed during an attempt to get into lunar orbit, NASA wanted to make sure that astronauts could loop around the moon and get back to Earth using gravity alone. This “free return” constraint limited Apollo landing sites to a narrow band north and south of the moon’s equator.
Robots don’t have the same worries about returning to Earth, and from orbit, the moon’s south pole is among the best-studied patches of lunar terrain. Three previous missions, including India’s Chandrayaan-1 orbiter, fired small impactors into the region’s surface to kick up debris clouds that orbiters overhead could analyse.
Even so, soft landings south of Chang’e-4 hadn’t been attempted before Chandrayaan-2, crewed or uncrewed—and as recent missions underscore, a lot can go wrong on the way to the surface. In April, the Israeli nonprofit SpaceIL’s Beresheet spacecraft crashed during the final moments of its lunar landing attempt. Had Beresheet pulled it off, it would have become the first privately funded spacecraft to land on the moon in a controlled manner.
In August, Sivan said that ISRO had learned lessons from Beresheet and other lunar landing attempts, noting that many other spacecraft have tried, and failed, to make it onto the moon in one piece. “One good thing is, we are learning from their failures,” he said.
Dhingra, who began his career with Chandrayaan-1, expressed hope that even the partial data from Vikram's descent could be salvaged.
“A decade of effort has gone into Chandrayaan-2, and I wish that we are able to extract everything that it has to offer, even if it's a failure of any sort,” he said in an email.
Though Vikram may not have landed softly, it is part of a bigger global wave of robotic lunar explorers. NASA has partnered with private companies to send scientific instruments to the moon, and countries including China, Russia, Japan, South Korea have plans to send spacecraft to the moon in the next decade.
In an interview before the landing attempt, Neal expressed optimism about the future of lunar exploration: “It’s exciting to see nations that weren’t involved in the space race of the ‘60s going to the moon,” he said. “It shows that we’re trying to get off this planet and explore—and it’s not just the United States or Russia. It’s other countries that are doing it, too.”
Lead Image: In July, India's Chandrayaan-2 mission launched toward the moon atop a GSLV MkIII-M1 rocket. On September 6, the mission's Vikram spacecraft attempted to land farther south than any other controlled lunar landing.
PHOTOGRAPH BY ISRO