Dropping a capsule from a probe is a bit like playing darts – but on a basketball court, says NASA manager Rich Burns. On Sunday, the NASA probe “Osiris-Rex” is scheduled to release the sample from the asteroid Bennu over the desert of the US state of Utah at an altitude of around 102,000 kilometers.
Hours later, the capsule will enter the Earth’s atmosphere protected by a heat shield and will touch down around 13 minutes later with the help of parachutes in an area approximately 58 by 14 kilometers in size. “It’s kind of like throwing a dart across a basketball court and hitting the bullseye on the other side,” Burns says.
If everything works out, it would be the first sample of an asteroid successfully brought to Earth in NASA’s history – and probably the largest such sample ever taken. “A piece of solar system history,” as Nasa scientist Nicola Fox says.
She and her colleagues estimate that there are around 250 grams of dust and debris in the capsule, which has a diameter of around 81 centimeters, weighs around 46 kilograms and looks like a kind of salad bowl with a high lid. In 2005, the Japanese space probe “Hayabusa” landed on an asteroid. In 2010, it brought the first soil samples ever collected from such a celestial body to Earth. There have been other flights to asteroids, but no other probe has yet brought material back to Earth.
Spectacular collection of the sample
The taking of the sample by “Osiris-Rex” (the abbreviation stands for: Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) in October 2020 was a complicated and spectacular maneuver lasting several hours: the probe had launched from the Cape Canaveral spaceport in 2016 temporarily left its place in Bennu’s orbit and approached it to within a few meters. Using a kind of robotic arm, she touched the asteroid’s surface for about five seconds, expelling pressurized nitrogen to stir up sample material, which was then sucked up.
A breakdown promptly occurred during the complex process, which had been practiced twice before: the lid of the collecting container was slightly pried open by larger stones, allowing parts of the sample to escape. The NASA scientists still assume that there is enough material in the collecting container.
After landing, the sample will be taken to NASA’s Johnson Space Center in Houston, Texas, for examination. The deep black Bennu, named after an ancient Egyptian deity, has a diameter of around 550 meters and could come quite close to Earth in a good 150 years. Even if the risk of impact is very low, NASA counts Bennu as one of the most dangerous asteroids currently known – and therefore wants to research it in detail.
New tasks await “Osiris-Rex”
The scientists also hope that the “Osiris-Rex” mission, which costs around a billion dollars, will provide insights into the formation of the solar system more than 4.5 billion years ago, because asteroids are remnants of it. The next NASA probe, “Psyche,” is scheduled to set off to an asteroid at the beginning of October.
The “Osiris-Rex” probe, which is around six meters long and weighs 2,100 kilograms, has already been assigned new tasks. After being dropped, it should fly directly to the next asteroid, this time to Apophis. According to calculations, the asteroid with a diameter of around 370 meters will fly past Earth at a distance of around 32,000 kilometers in 2029 and could therefore be studied up close for the first time. “Osiris-Rex” also gets a new name for the follow-up mission: “Osiris-Apex”.
