Tech: NASA's only mission to the Asteroid Belt is dying after 11 years in space — but it might tee up the future discovery of alien life

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An illustration of NASA's Dawn spacecraft flying toward Ceres using its ion thrusters.

In 2007, NASA launched an ion-propelled probe called Dawn toward the Asteroid Belt. It has visited a huge asteroid called Vesta and a Texas-size dwarf planet called Ceres, which may hide a salty ocean (and possibly alien life). But the spacecraft is almost out of fuel and may die in September.

  • NASA launched an ion-propelled probe called Dawn toward the Asteroid Belt in 2007.
  • In 2015, Dawn reached Ceres — a Texas-size dwarf planet that may hide a salty ocean and possibly alien life.
  • The spacecraft is almost out of fuel, and its mission may end between mid-September and mid-October.
  • Researchers expect Dawn to stay in orbit for 20 to 50 years, but after that it may crash into Ceres.
  • On Friday, NASA hosted a live chat about Dawn's discoveries and coming end.

NASA's only robot exploring the Asteroid Belt is about to die, the space agency explained during a live event on Friday.

However, a last-ditch maneuver it pulled off this summer is helping create surface maps of a dwarf planet, information that may be used to land a sample return mission on the distant world.

The Dawn probe launched in 2007 and became the first NASA mission to use super-efficient ion thrusters on a years-long voyage through deep space. The robot ended up in the Asteroid Belt, the mysterious and expansive zone between Mars and Jupiter, where it has studied the region's two largest objects: Ceres and Vesta.

Dawn reached Vesta first, in July 2011. Vesta is the second-largest object in the Asteroid Belt; researchers think it of it as a "time capsule" for planet formation, since it failed to grow into something larger after the solar system's birth.

After a year of exploration at Vesta, Dawn ion-propelled itself toward a Texas-size dwarf planet called Ceres, where it arrived in March 2015. Ever since then, Dawn has made a number of major discoveries about the 592-mile-wide ice ball, including an ice volcano, shiny salt deposits, and other features that suggest a giant ocean may hide beneath the world's cratered crust — possibly one that could harbor alien microbes.

NASA has since used up most of Dawn's remaining fuel to slip into an orbit that zooms within 22 miles of Ceres' surface about once a day.

These close flybys are about 10 times closer than the International Space Station orbits above Earth and have led to the sharpest, clearest images of the dwarf planet yet.

"This orbit was like putting your glasses on if you don't see very well. All of the sudden, all of this rich detail is popping out," Carol Raymond, Dawn's principal investigator and a planetary scientist at NASA's Jet Propulsion Laboratory, said on Friday during a press event. "It will give us some insight as to what's going on with the plumbing system under the surface."

However, these unprecedented images and other data have come with a cost: A death for Dawn before the end of the year.

Why Dawn is now doomed

Using up Dawn's fuel to achieve such a close orbit has essentially stranded the spacecraft around Ceres.

"The current orbit should be stable for 50 years," Mark Sykes, director of the Planetary Science Institute and a scientist on the Dawn mission, told Busines Insider in an email. "There is no desire to change the orbit — and no juice."

Dawn uses its "juice" to keep itself powered and talking to NASA. So using up the last propellant will forever silence the probe.

"It will struggle for a short time, but it will be impotent," Marc Rayman, Dawn's mission manager and chief engineer, wrote in a blog post on August 22. "Unable to point its electricity-generating solar panels at the sun or its radio antenna to Earth, the seasoned explorer will go silent and will explore no more. Its expedition will be over."

That expedition was supposed to last nine years, but it has been nearly 11 years. So the team, while sad about the probe's coming demise, is counting its blessings — especially because Dawn continues to take high-resolution images of the surface once every 27 hours.

Rayman said on Friday that Dawn may go silent within a month or so.

"We can't determine that with exquisite accuracy," he told Business Insider during the press event, adding that it's most likely to run out of propellant (and stop talking to Earth)" sometime in the middle of this month to the middle of October."

Once the probe runs out of fuel, it shouldn't spiral down and crash into Ceres for at least 20 years. In fact, Rayman added that the team crunched the numbers, and their analysis shows a "greater than 99%" chance that Dawn will stay in its current orbit for half a century, "and most likely longer than that."

NASA wants to bring a sample of Ceres back to Earth

Rayman says the 20-year no-crash minimum was a core requirement of the Dawn mission.

That's because NASA's planetary protection office — which tries to prevent contamination of other worlds by microbes from Earth — thinks this should provide the agency enough time to mount another mission to explore the surface of Ceres.

Such a hypothetical mission could look for signs of life without worrying about Dawn's wreckage — and contamination by any microbes from Earth that are stuck to the robot.

"Ceres represents a place in the solar system that we're interested in for future astrobiological exploration," Rayman said. "If NASA chooses to mount a follow-on mission to conduct subsequent astrobiological exploration, it's long enough to without being compromised by Dawn."

Jim Green, NASA's chief scientist, said the agency has pulled together working groups to come up with a plan to send a robot to the surface of Ceres, possibly near a vent, where it can probe salts and other materials — and maybe even launch samples of the dwarf planet back to Earth.

"We'll work out the next decade whether one of those missions will indeed be going back to Ceres," Green said on Friday.

The stakes are high as researchers discover more and more water and organic compounds elsewhere in the solar system — ingredients that may sustain rudimentary forms of alien life.

"We know there is an active geological cycle that's bringing material from on deep up to the surface," Carol Raymond said. "That gives us an opportunity to sample some of Ceres' internal material."

As Dawn continues to rack up high-resolution images of the surface, the argument for collecting a sample of Ceres may grow.

"The holy grail of any planetary science mission is a sample return, but it's also very difficult," Raymond said. "With an object like Ceres, you really want to know where to sample."

This story has been updated with new information. It was originally published at 1:27 p.m. EDT on September 7, 2018.

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