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Image source, NASA / Goddard / UoA
Illustration: Osiris-Rex approaching the surface of the asteroid Bennu.
The American Osiris-Rex spacecraft has completed a daring maneuver designed to briefly touch the surface of an asteroid and collect samples from it.
Radio signals sent to Earth from a distance of 330 million kilometers confirmed Tuesday that the spacecraft had made contact with the 500-meter-wide object known as Bennu.
But the NASA-led mission will have to wait for more data from Osiris-Rex before knowing for sure that the material was actually collected.
The goal was to acquire at least 60g, perhaps even a kilo or more.
But why are samples from this asteroid so important?
Key milestone
“The emotions are running high, everyone is really proud,” said the mission’s principal investigator, Dante Lauretta, of the University of Arizona, Tucson.
“This was the key milestone of this mission. Now there are a few days to find out how much we got from this amazing sample, which we have been thinking about for decades,” added Thomas Zurbuchen, associate administrator for science at NASA.
Both men were following events from the mission control base at the Lockheed Martin spacecraft manufacturer in Maryland, USA.
Congratulations to the entire @OSIRISREx team and all the partners of the @NASA on this mission! We are on our way to bring the largest space specimen brought home from Apollo. If all goes well, this sample will be studied by scientists for generations to come!Jim Bridenstine, NASA Administrator, tweeted.
Because Bennu is a very primitive space object, scientists believe that the sand and dust on its surface could hold fascinating clues about the chemistry that gave rise to the Sun and the planets more than 4.5 billion years ago.
Assuming Osiris-Rex has collected a suitable sample, the spacecraft will be able to package it to return with it to Earth in 2023, after spending seven years in space.
The ship was launched in September 2016 and arrived at Bennu in December 2018.
If the ship didn’t collect anything Tuesday, the mission team will have to set up Osiris-Rex for another attempt in January.
But how was the maneuver you performed?
“Reverse vacuum cleaner”
The ship made its attempt to collect a sample in a narrow piece of land in northern Bennu called Nightingale.
Osiris-Rex slowly descended to the eight-meter-wide target area over a period of four and a half hours, passing towering rocks along the way, including a two-story-tall block that had been dubbed Mount Doom.
Osiris-Rex used what some have described as a “reverse vacuum” to capture material from the surface.
More correctly called the Sample Acquisition Mechanism Touch and goTag-Sam, or Tag-Sam, is a 3.35 meter long arm with a ring-shaped collection chamber at the end.
The idea was to bring the ring closer to the surface and, at the same time, Expulsar a stream of nitrogen gas to lift small rock fragments and get them trapped in the collection chamber.
Sensors on Osiris-Rex informed mission controllers that all actions in the sampling sequence had been completed successfully and that the spacecraft had moved away from Bennu as planned after a few seconds of contact.
Measurements
The science and engineering team will need time to assess what exactly may have been trapped in the collection chamber.
One way to do this is to photograph the head of the ring, which will be done in the next few days.
Image source, NASA / Goddard / UoA
Bennu has preserved materials from the beginning of the Solar System.
But the controllers will also order the ship to turn with the Tag-Sam arm and ring extended.
Any additional mass on board will change the amount of momentum required for the spin, compared to the amount needed to perform the same spin exercise prior to sample acquisition.
This measurement technique will give results accurate to within a few tens of grams.
Osisris-Rex took photographs throughout its descent, but was unable to send any of them home at the time because its antenna was not pointed at Earth.
Once the ship re-establishes this connection, the data can be transferred.
“Those images are going to give us a huge amount of information about how today’s events were,” said Professor Lauretta. “They will give us information on the probability of collection of samples, that is, a kind of probabilistic evaluation.”
NASA promises to publish some of these images on Wednesday.
Many scientists, including in the UK, are hoping to have the opportunity to analyze any material brought back from Bennu, including Sara Russell from the Natural History Museum in London.
“Asteroids like Bennu were formed in the early days of the Solar System. They are basically the building blocks of planets, a time capsule that will tell us how the Sun and planets arose and evolved. Bennu can really help us dig deeper into how that process happened, “he told BBC News.
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