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Explained: NASA’s OSIRIS-REx mission successfully picks samples from asteroid Bennu, but there is a problem

Days after the spacecraft first touched the surface of asteroid Bennu, located over 200 million miles away from Earth, the coordinators of the mission are now saying that it may have performed too well.

Asteroid Bennu, OSIRIS-REx, NASA asteroid Bennu,US spacecraft, Us spacecraft asteroid, rare rubble grab, science, asteroidThis image shows the OSIRIS-REx spacecraft's primary sample collection site, named "Nightingale," on the asteroid Bennu. (NASA/Goddard/University of Arizona via AP)

NASA’s OSIRIS-REx spacecraft, which was sent to collect rocks and dust from the surface of a near-Earth asteroid, is now so stuffed with cosmic rubble that a door was wedged open and precious samples are presently leaking into space.

Days after the spacecraft first touched the surface of asteroid Bennu, located over 200 million miles away from Earth, the coordinators of the mission are now saying that it may have performed too well.

“The big concern now is that particles are escaping because we’re almost a victim of our own success,” Dante Lauretta, the mission’s principal investigator at the University of Arizona in Tucson, said during a NASA press briefing on Friday.

So, what is happening with the mission now?

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When the team behind the mission analysed images taken of the spacecraft’s collector head they realised that it had gathered far more samples than they had anticipated. So much so that the large rocks and rubble had jammed the flap that was designed to keep the samples inside the sample container.

On Tuesday, NASA TV reported that the spacecraft’s robotic arm, also called the Touch-And-Go Sample Acquisition Mechanism or Tagsam, had made contact with the surface of the ancient Bennu asteroid. While mission planners expected the total time of contact to be less than 16 seconds, the actual period of contact was a mere six seconds and most of the sample was collected within the first three seconds.

The robotic arm penetrated deeply into the surface of the asteroid with such force that several large rocks were wedged around the rim of the container’s lid. As a result, particles are now spilling over and escaping into space.

The mission was required to collect a minimum of 2 ounces, or 60 grams, of rocks and dust from the asteroid’s surface. But researchers now believe that the arm captured at least 400 grams of material.


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What is NASA doing to minimise damage?

NASA is now scrambling to minimise the damage and rushing to stow the collection container within the spacecraft well ahead of schedule. “A substantial fraction of the required collected mass is seen escaping,” Lauretta explained.

To preserve what is left of the surface material, the mission team has decided to cancel activities planned this weekend to prevent more sample loss due to excessive movement. Both, a braking burn, which was scheduled for Friday, and a measurement of the sample’s mass on Saturday were called off this week.


While they are uncertain about the exact loss rate, researchers believe that the craft is continually losing an estimated 5 to 10 grams of material.

“We are working to keep up with our own success here, and my job is to safely return as large a sample of Bennu as possible,” Lauretta said. “The loss of mass is of concern to me, so I’m strongly encouraging the team to stow this precious sample as quickly as possible.”📣 Follow Express Explained on Telegram

Despite hastening the process, the craft will not be returning to Earth before 2023. It is only then that the team will be able to measure out the samples collected. But they are confident that they have enough.

But, what is asteroid Bennu?

Asteroid Bennu was first discovered by a team from the NASA-funded Lincoln Near-Earth Asteroid Research team in 1999. It was named after an Egyptian deity by a nine-year-old boy from North Carolina in 2013 who won NASA’s “Name that Asteroid” competition.

Located around 200 million miles away from Earth, asteroid Bennu is around the size of the Empire State Building in New York.


Significantly, Bennu hasn’t undergone drastic changes since its formation over billions of years ago and, therefore, it contains chemicals and rocks dating back to the birth of the solar system. It is also relatively close to the Earth.

In 2016, NASA launched the OSIRIS-REx — Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer — mission to collect samples of pebbles and dust from the surface of the ancient asteroid for the first time in history.


It reached its target in 2018 and since then, the spacecraft has been trying to match the velocity of the asteroid using small rocket thrusters to rendezvous it. During this time it also surveyed the surface to identify sites from which it could collect samples.

The spacecraft contains five instruments meant to explore Bennu including cameras, a spectrometer and a laser altimeter. The departure window for the mission will open up in 2021, after which it will take over two years to reach Earth.

First published on: 25-10-2020 at 12:30:19 am
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