NASA says small asteroid could hold grand answers
Mission to Bennu aims to capture clues to life’s origin
Get ready for an interplanetary treasure hunt.
On Thursday, NASA will launch its first mission to visit an asteroid and bring precious samples back to Earth.
OSIRIS-REx, set to launch around 7:05 p.m. EDT, will head to Bennu, a dark rubble-pile of an asteroid that stretches1,614 feet wide.
After the spacecraft reaches and orbits the near-Earth asteroid in 2018 and carries samples back to Earth, scientists hope to develop a detailed profile to shed light on the early evolution of the solar system, clues to the origin of life and tools that will allow them to accurately track asteroids that come uncomfortably close to Earth.
The spacecraft, aboard an Atlas V rocket, was rolled out to the launch pad Wednesday. “We’re ready to go,” said Jason Dworkin, the mission’s project scientist, “and excited to see the spacecraft fly.”
OSIRIS-REx — short for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer — is bringing a suite of instruments that will help it understand Bennu in unprecedented detail. It will use several cameras to examine the surface, a laser altimeter to map the 3-dimensional topography, visible- and infrared-light spectrometers to study its chemical and mineral composition and an X-ray spectrometer to study elemental abundances.
It also holds an arm with a disc-like device at the end that will carefully contact the surface and collect some of the dust and rock that scientists think cover Bennu’s surface. “We are basically a space vacuum cleaner,” principal investigator Dante Lauretta said in a briefing Wednesday.
The eight known planets formed when the solar system was still in its infancy, coalescing out of the swirling disc of gas and dust that surrounded our nascent star. The asteroids are those bits of rock that never quite made it into one of these worlds; scientists think the belt of debris that stretches between the orbits of Jupiter and Mars could have been a planet, had the gas giant’s gravity not kept it from forming.
These asteroids, then, are the leftover building blocks of the solar system — rocks that have never been altered by the heat and pressure inside a planet or been chemically transformed by the presence of life. As such, they hold clues to the early development of the solar system.
Bennu is particularly intriguing because its dark surface indicates that it’s full of organic molecules, the kinds of chemicals that could have seeded life on Earth.
Researchers have studied pieces of asteroids that have fallen to Earth as meteorites, but their plunge through the atmosphere and contact with the planet contaminates them so that it’s difficult to tell what chemical clues are from the sample and which ones are terrestrial contamination.
Bennu will also allow scientists to study the Yarkovsky effect, a strange phenomenon that especially affects smaller, darkcolored asteroids. The asteroid’s surface absorbs sunlight and then re-emits it later as heat, which acts like a thruster and can alter its course.
This makes it difficult to predict an asteroid’s path; for example, Dworkin pointed out, Bennu has veered about 60 miles off course since its discovery in 1999. Learning in detail how the Yarkovsky effect acts on Bennu could help scientists better predict the trajectories of other asteroids whose paths bring them within striking distance of Earth.
“If you want to be able to predict where an object like Bennu is going to be in the future, you have to account for this phenomenon,” Lauretta said.
As it is with most interplanetary missions, patience is key: Scientists will have to wait to analyze the sample Bennu carries back to Earth; the spacecraft isn’t slated to return its cargo until 2023.
An artist’s rendering shows the OSIRIS-REx spacecraft approaching Bennu. The mission is to launch Thursday.