This little Mars helicopter has opened a new frontier in space exploration

On a bright red day on Mars last year, a pint-size helicopter little bigger than a child’s toy lifted off and ascended 10 feet high above an ancient crater.

In that 39-second flight on April 19, 2021, NASA’s Ingenuity helicopter became the first aircraft to fly on another world. Now facing the Martian winter, it has graduated from a prototype to driving scout for a nuclear-powered rover traversing the 3.5-billion-year-old terrain of Jezero Crater. The helicopter’s success has would-be planetary explorers pondering whether such craft could be used on other worlds with atmospheres throughout the solar system, like Venus and Titan, Saturn’s moon, as well as gas giants like Jupiter and Saturn.

The idea of taking space exploration to the skies to reveal some of the solar system’s hidden realms — caves, canyons and craters until now barred from exploration — has already opened eyes at NASA.

“An enormous success, really, beyond what we ever anticipated in the beginning,” said Dave Lavery, program executive for the Ingenuity Mars Helicopter. The helicopter team had hoped to get five test flights out of the 4-pound (1.5 pounds on Mars), two-rotor drone before it died. Instead, said Lavery, “we have a machine that is working very well, that is a demonstrated capability for surviving in the environment we have on Mars, right now.”

Ingenuity’s flight ranks with the rolling out of 1999′s Mars Sojourner, a small, tethered rover that persuaded NASA that wheels were the way to explore Mars, said Lavery. Aerodynamic predictions for the helicopter worked perfectly, making planning easier for future contemplated 44-pound science copters (“Physics works the same everywhere in the solar system,” he said.) By going from prototype to scout, Ingenuity points to a likely next step for flyers on Mars — as guides for rovers. It also has served as “a reality check” on some of the more ambitious ideas proposed for mapping the red planet from the air, as scientists try to figure out if life ever evolved on Mars and how its once wet atmosphere wasted away to today’s cold, arid world. “We’ve looked at a lot of different sorts of concepts, and I think right now what we’re doing is saying, ‘OK, a lot of these are very real.’”

Congress agrees. A House budget committee in June called for NASA to add “more than one” Ingenuity-like helicopter to a mission planned to retrieve rock samples from Mars. A University of Arizona project funded by NASA is this month headed to Iceland to test-run just such a sample-retrieval mission on the fresh lava field of a recent volcano.

New vistas on Mars

Three rovers, two American and one Chinese, are right now rolling on Mars. Until Ingenuity, rover exploration had been a trade-off between risks and rewards, said Joel Davis, a planetary geologist with Birkbeck, University of London. Driving to the most intriguing places, say a cliff face or deep into a curious crater, might strand your explorer.

A sand trap ended NASA’s Spirit rover mission in 2009 (“a golfer’s worst nightmare,” said an agency official), for example, and scientists scouted a small crater for months, from space, before letting the Opportunity rover descend in 2007. Right now, NASA’s Perseverance rover has a rock stuck in its front left wheel, and the 9-year-old aluminum wheels on the Curiosity rover have holes punched in them from rocks.

For two decades, Mars landing sites have been constrained to flat, smooth plains amenable to safe driving, keeping them on the northern half of the planet. But flat places are not where the action is in geology, said Davis. Cliffs are. “It’s often frustrating that rovers are unable to access many of these regions,” he said.

Future Mars helicopters won’t face those barriers — they could even start exploring places like Valles Marineris, the 1,800-mile-long “Grand Canyon of Mars.” Billions of years of geological history are recorded there in mountains and cliff walls, some up to 5 miles high.

A “Mars Science Helicopter” proposed by the Jet Propulsion Laboratory, for example, might fly over the planet’s rocky southern highlands. Those are home to the planet’s most ancient landscapes. Flying up and down cliffs, its mission would be to uncover just when Mars lost most of its atmosphere billions of years ago, transforming it into today’s dust-swirled wasteland.

Even further ahead, future Mars astronauts might deploy small helicopters to retrieve rock samples or look over terrain for safety, said Lavery: “We should start thinking about these as not just unique, singular, devices but perhaps pairs, or trios, or even swarms of these flying devices, to do tasks on the surface of planets.”

Could a helicopter even carry an astronaut on Mars someday? “Using today’s technology, I’d have to say no,” said Lavery. “But there may be some future technologies that we develop in the next couple of decades that may entirely change that answer.”

The best place to fly in the solar system

Ingenuity’s success has sparked a lot of optimism on the one NASA mission, called Dragonfly, already set to fly a helicopter on a different world — Saturn’s haze-shrouded moon, Titan — in 2034.

“I’m honestly surprised Ingenuity flew so well. Mars is a terrible place to fly,” said Catherine Neish, a research scientist with the Planetary Science Institute who is working on the Dragonfly mission. Titan might be a better place to fly than Earth, in truth, with air four times as thick and gravity less than the moon’s. “So, if you can get it to work on Mars, we should be in great shape,” said Neish.

Unlike Ingenuity, the Dragonfly mission will be a full-fledged science lab in flight: a roughly 926-pound (132 pounds on Titan) octocopter powered by a nuclear battery, with sensors equipped in its landing skids. “Dragonfly is more like Curiosity or Perseverance,” said Elizabeth “Zibi” Turtle of the Johns Hopkins University Applied Physics Laboratory (APL), principal investigator on the mission scheduled for launch in 2027. “Really the difference is that we fly to get from place to place instead of instead of driving across the surface. But we’re really more like [a rover] in terms of the science payload and the measurements that we’ll be making.”

Although the European Space Agency’s Huygens probe briefly sent one landing picture back from Titan in 2005, the landscape there is a bit of a mystery, said Turtle. Shrouded by thick haze, the moon’s bedrock is ice weathered by liquid methane rain. Warmed by its nuclear battery, Dragonfly is expected to explore a frozen dune near a crater to start its mission.

“Titan has this wonderfully big thick atmosphere,” said Ralph Lorenz, mission architect on Dragonfly, and also of APL. “You can just throw your spacecraft at it,” he said, to slow down to parachute-friendly speeds. The other icy moons of the solar system, such as Europa circling Jupiter or Enceladus circling Saturn, would require big and expensive rockets to land a probe. “It’s really what makes this mission affordable,” said Lorenz.

Gravity is so low, and the atmosphere so dense, that an astronaut on Titan could in fact fly just by flapping glider wings to stay aloft. However, it’s a little on the cold side with surface temperatures of -297 degrees Fahrenheit.

Flying the friendly alien skies

Edgar Rice Burroughs and the pulp novels of the last century embraced the notion of flying on other worlds, in swords-and-sandals epics. But space mission planners have thought seriously about the idea for decades, said Lorenz, first contemplating balloons or airships to explore Titan, buoyed by its thick atmosphere.

“Airships would work fine on Titan,” he said. “You just sit there, and that’s great.” But the trouble is with the ground, where a stray gust might crash your multimillion-dollar space mission while it is investigating a site up close. Or if its samplers get snagged, an airship is essentially anchored.

Space scientists have also proposed airplanes for both Mars and Titan, as well as Venus, which has an upper atmosphere 34 miles above its surface that is similar to Earth’s, sulfuric acid clouds excepted.

Helicopters still look like the winners when it comes to flying on other worlds for all those reasons. The space agency has benefited from the revolutionary growth in drone copters in the last decade, advancing everything from controls to batteries to designs to materials, said Lavery: “It’s only been in the past 10 years that the technology has advanced enough that we’ve been able to build a package that was lightweight enough that we actually could make it happen.”

Still, the rarity of atmospheres throughout the solar system — only eight worlds have appreciable ones — will always keep aircraft niche solar system explorers, said Lorenz. It’s a good niche, though. “You could build Dragonfly all over again and send it to some really interesting places on Titan. Right now, we have mobility that is transformational, vastly in excess of what planetary rovers on the Moon or Mars have been able to do. You can talk about going hundreds of kilometers in a few years,” he said.

And the air might not be a last frontier for planetary exploration: A successor to Dragonfly might be the first watercraft on another world, equipped with pontoons instead of skids to explore the methane seas girdling that moon.

For now, Ingenuity is still running, with a 30th mission planned. The $85 million helicopter survived a lost communications scare tied to lower power from its solar cells as the Martian winter encroached, and the loss of a device that measures its tilt before taking off. Both problems are surmountable by lowering its heating temperature and with a software patch, but Lavery conceded the helicopter’s days are numbered.

Should Ingenuity shut down tomorrow, he added, the helicopter has so far outlived expectations that the mission team would feel “ecstatic” anyway, while it plans for the next Mars helicopter.

“We have an entire planet that is waiting to be explored by these types of robotic devices,” Lavery said. “We believe in these sorts of craft as partners for an eventual, human mission to the surface of Mars.”

Thanks to Lillian Barkley for copy editing this article.