LAST UPDATE | 24 Sep 2023
A SEVEN-YEAR space voyage has come to a climactic end after a NASA capsule landed in the desert in the US state of Utah, bringing with it the largest asteroid samples ever collected.
Scientists have high hopes for the sample, saying it will provide a better understanding of the formation of our solar system and how Earth became habitable.
“Touchdown of the Osiris-Rex sample return capsule!” a commentator said on NASA’s live video webcast of the landing, as engineers and team members applauded at a nearby mission control center.
Completing a 6.21 billion-km journey, the touchdown marked the United States’ first sample return mission of its kind, the US space agency said.
NASA chief Bill Nelson hailed the mission and said the asteroid dust “will give scientists an extraordinary glimpse into the beginnings of our solar system”.
The Osiris-Rex probe’s final, fiery descent through Earth’s atmosphere was perilous, but NASA managed to engineer a soft landing at 8:52 am local time (2.52pm Irish Time), in the military’s Utah Test and Training Range.
Four years after its 2016 launch, the probe had landed on the asteroid Bennu and collected what NASA estimated is roughly 250 grammes of dust from its rocky surface.
Even that small amount, NASA says, should “help us better understand the types of asteroids that could threaten Earth”.
The sample return “is really historic,” NASA scientist Amy Simon told the AFP news agency.
“This is going to be the biggest sample we’ve brought back since the Apollo moon rocks” were returned to Earth.
Osiris-Rex released its capsule early Sunday from an altitude of more than 100,000km.
The fiery passage through the atmosphere came only in the last 13 minutes, as the capsule hurtled downward at a speed of more than 43,000 kilometres per hour, with temperatures of up to 2,760 degrees Celsius.
Its rapid descent was supposed to be slowed by two successive parachutes as it made its way to the 60km by 14km landing zone.
The main chute, however, deployed “much higher than was originally anticipated,” at about 6,100 metres rather than 1,500 metres, NASA said.
NASA images showed the tire-sized capsule on the ground in a desert wash, with scientists approaching the device and taking readings.
Eventually they concluded the capsule was not breached, meaning its all-important air-tight seal remained intact, avoiding any contamination of the sample with desert sands.
The team then lifted the capsule by helicopter to a nearby “clean room”.
Meanwhile, the probe that made the space journey fired its engines and shifted course away from Earth, NASA said, “on its way” for a date with another asteroid, known as Apophis.
Scientists predict that asteroid will come within 32,000km miles of Earth in 2029.
On Monday, the sample will head to Johnson Space Center in Houston for additional study, and NASA plans to announce its first results at a news conference 11 October.
Most of the sample will be conserved for study by future generations. Roughly one-fourth will be immediately used in experiments, and a small amount will be sent to mission partners Japan and Canada.
Japan had earlier given NASA a few grains from asteroid Ryugu, after bringing 0.2 ounces of dust to Earth in 2020 during the Hayabusa-2 mission. Ten years before, it had brought back a microscopic quantity from another asteroid.
But the sample from Bennu is much larger, allowing for significantly more testing, Simon said.
Asteroids are composed of the original materials of the solar system, dating back some 4.5 billion years, and have remained relatively intact.
They “can give us clues about how the solar system formed and evolved,” said Osiris-Rex program executive Melissa Morris.
“It’s our own origin story.”
By striking Earth’s surface, “we do believe asteroids and comets delivered organic material, potentially water, that helped life flourish here on Earth,” Simon said.
Scientists believe Bennu, about 500 meters in diameter, is rich in carbon – a building block of life on Earth – and contains water molecules locked in minerals.
Bennu surprised scientists in 2020 when the probe, during its brief contact with the asteroid’s surface, sank into the soil, revealing an unexpectedly low density, like a children’s pool filled with plastic balls.
Understanding its composition could come in handy in the – distant – future.
For there is a slight, but non-zero, chance (one in 2,700) that Bennu could collide catastrophically with Earth, though not until 2182.
But NASA last year successfully deviated the course of an asteroid by crashing a probe into it in a test, and it might at some point need to repeat that exercise — but with much higher stakes.
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