A view of eight sample trays containing the final material from asteroid Bennu. The dust and rocks were poured into the trays from the top plate of the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) head./Erika Blumenfeld & Joseph Aebersold/Supplied
It’s barely a teaspoon’s worth of black dirt – 4.864 grams to be exact – but for Canadian planetary scientists and their colleagues it adds up to a world of possibilities.
On Thursday, officials revealed the precise size of the portion of the asteroid Bennu that has been designated for Canada as part of the country’s participation in OSIRIS-REx, a NASA-led mission to capture and return material from the distant body for scientific analysis.
As part of its flight plan, the spacecraft briefly made contact with the asteroid’s gravelly surface back in October, 2020. A sealed capsule with the material it collected then was later sent to Earth, arriving at a landing site in Utah last September.
However, once the capsule was transported to the Johnson Space Center in Houston Tex., for examination, scientists ran into a snag. The screws on the container that held the bulk of the sample were too tight. The container could not be opened inside the specially prepared glovebox that scientists were working with in order to avoid contaminating the extraterrestrial material.
Now, with the help of a new tool, the container has been opened and scientists found a total of 121.6 grams of dark, gritty matter from the asteroid. It is the largest sample by far to come from beyond the moon and more than twice what was required to declare mission success.
Canada’s share was previously determined to be four per cent of whatever OSIRIS-REx brought back. A part of that amount has already been set aside and stored to preserve its pristine characteristics. Canadian Space Agency officials said the remainder would be selected once the properties of the entire sample are better understood. The total share more than meets Canada’s goals for the mission.
“It’s a great success,” said Caroline-Emmanuelle Morisset, a program scientist with the agency who is involved in preparing a curation facility at the agency’s headquarters in Longueuil, Que., where the portion will eventually reside.
Dr. Morisset said the darkness of the material is a sign that its mineral constituents are especially rich in carbon, including the molecules that are precursors to those that could have once given rise to life – a key reason why Bennu was chosen as a target for the mission.
She added that the material also contains “little specks that are more sparkling,” which are made of sulphur-bearing minerals. The overall composition of the sample shows that its constituents formed in the presence of water, likely when Bennu was part of a larger asteroid that was later shattered by a collision of space rocks.
Kim Tait, who is senior curator of mineralogy at the Royal Ontario Museum in Toronto, said that the Bennu sample is similar to carbon-rich meteorites that have landed on Earth, and to a smaller sample retrieved by a Japanese asteroid mission. But it has differences that put it in a class by itself and that hint at some diversity in the raw materials from which Earth and other planets were built.
“The fact that it’s not exactly like the other stuff we’ve seen is, I think, a good sign,” Dr. Tait said.
Canada’s share of Bennu is expected to arrive in 2025, at which point researchers can apply to conduct studies of the material. A much smaller amount of the asteroid made a visit to the country last month, when planetary scientist Ed Cloutis temporarily received 200 milligrams of powdery material to conduct reflectance tests in his laboratory at the University of Winnipeg.
“It was very dark – kind of like charcoal,” said Dr. Cloutis. His results showed that the substance was similar in its light-reflecting properties to what the spacecraft observed more broadly when it was in orbit around Bennu.