Nav: Home

NASA instrument to use X-rays to map an asteroid

July 12, 2016

NASA's OSIRIS-REx spacecraft will launch September 2016 and travel to the near-Earth asteroid Bennu to harvest a sample of surface material and return it to Earth for study. But before the science team selects a sample site, they can find out a bit about Bennu's elemental make-up.

To determine the composition of Bennu's surface, the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) team equipped the spacecraft with an instrument that will identify which elements are present on the asteroid and measure their abundance.

The Regolith X-ray Imaging Spectrometer, or REXIS can image X-ray emission from Bennu in order to provide an elemental abundance map of the asteroid's surface.

"REXIS is different from the other imaging instruments on OSIRIS-REx because we're going to determine what Bennu is made of at the level of individual atomic elements," said Richard Binzel, REXIS principal investigator and instrument scientist at the Massachusetts Institute of Technology (MIT), Cambridge. "We're sniffing the atoms on the surface of Bennu."

To do that, REXIS gets a little help from the sun. Atoms on Bennu's surface absorb incoming solar X-rays that are emitted along with the solar wind. This causes electrons in the atom to move to a higher energy level. However, because these excited electrons are unstable, they quickly de-excite and drop back down to their original energy level and emit their own X-ray in turn. This process is known as fluorescence.

"You have all this energy coming in, and it kicks electrons up to the next energy level, but the electrons quickly decay back down and emit X-rays of precisely that same energy," said Josh Grindlay, REXIS co-principal investigator and deputy instrument scientist at Harvard University, Cambridge, Massachusetts. "The net result is a glowing surface on Bennu."

The energies of the re-emitted X-rays are characteristic of the elements from which they came. Elements absorb and re-emit X-rays at different, specific energies. The energies that the science team will see glowing at Bennu's surface will tell the researchers which elements are present.

In order to map these emitted X-rays, REXIS is fitted with what's known as a coded aperture mask. The mask consists of a pattern of pinholes that, when X-rays shine through, creates a shadow pattern on REXIS' detector.

Imagine sitting in your bedroom at night and a car drives by. The headlights cast a pattern of light and shadow on the walls. As the car moves, so do the shadows. In REXIS' case, it's the spacecraft that moves over the asteroid surface. The changing shadow patterns allow the team to identify any particular bright spots on Bennu that might be especially abundant in a certain element.

REXIS was selected as a Student Collaboration Experiment for the OSIRIS-REx mission. Built by a team from MIT and Harvard, students will perform data analysis of REXIS as part of their coursework.

"This has been an amazing experience for the students," said Rebecca Masterson, REXIS co-principal investigator and instrument manager at MIT. "They get to see how a mission evolves and what it takes to get to the point of launch. They're getting to see how an idea goes from conception to completion and actually play a role in its success."

More than 100 students will have been involved in REXIS upon the completion of the OSIRIS-REx mission.

"Even though OSIRIS-REx hasn't left the ground, I think REXIS is already a success," said David Miller, NASA's chief technologist and a former REXIS team lead at MIT. "We've inspired so many students. They are our next generation of space scientists and engineers, and they've already had a profound impact on our abilities to go further and explore deep space."
Goddard provides overall mission management, systems engineering and safety and mission assurance for OSIRIS-REx. Dante Lauretta is the mission's principal investigator at the University of Arizona. Lockheed Martin Space Systems in Denver built the spacecraft. OSIRIS-REx is the third mission in NASA's New Frontiers Program. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages New Frontiers for the agency's Science Mission Directorate in Washington.

For more information about OSIRIS-REx, visit:

NASA/Goddard Space Flight Center

Related Asteroid Articles:

Queen's University scientist warns of asteroid danger
A leading astrophysicist from Queen's University Belfast has warned that an asteroid strike is just a matter of time.
New study ranks hazardous asteroid effects from least to most destructive
If an asteroid struck Earth, which of its effects -- scorching heat, flying debris, towering tsunamis -- would claim the most lives?
Wrong-way asteroid plays 'chicken' with Jupiter
For at least a million years, an asteroid orbiting the 'wrong' way around the sun has been playing a cosmic game of chicken with giant Jupiter and with about 6,000 other asteroids sharing the giant planet's space, says a report published in the latest issue of Nature.
Ceres hosts organic compounds, and they formed on the asteroid, not beyond
Aliphatic organic compounds -- carbon-based building blocks that may have a role in the chemistry that creates life -- have been detected for the first time on Ceres, an asteroid and dwarf planet, a new study reveals.
It's a bird... It's a plane... It's the tiniest asteroid!
A team led by UA astronomer Vishnu Reddy has characterized the smallest known asteroid using Earth-based telescopes.
NASA to map Asteroid Bennu from the ground up
The OSIRIS-REx Laser Altimeter, or OLA will be used to create three-dimensional global topographic maps of Bennu and local maps of candidate sample sites.
NASA to map the surface of an asteroid
NASA's OSIRIS-REx spacecraft will travel to near-Earth asteroid Bennu to sample surface material and return it to Earth for study.
NASA instrument to use X-rays to map an asteroid
NASA's OSIRIS-REx spacecraft will launch September 2016 and travel to the near-Earth asteroid Bennu to harvest a sample of surface material and return it to Earth for study.
New type of meteorite linked to ancient asteroid collision
An ancient space rock discovered in a Swedish quarry is a type of meteorite never before found on Earth, and likely a remnant of a massive asteroid collision 470 million years ago that sent debris raining to Earth.
Scientists reconstruct the history of asteroid collisions
An international study, in which Spain's National Research Council (CSIC) participates, reveals that asteroids have endured a multitude of impact strikes since their formation 4,565 million years ago.

Related Asteroid Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...