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OSIRIS REx: Asteroid Sample Return

Just over a year from now, we’ll be anticipating the launch of the OSIRIS-REx mission, scheduled to rendezvous with the asteroid Bennu in 2018. This will be the first American mission to sample an asteroid, and it’s interesting to note that the materials scientists hope to return will constitute the largest sample from space since the days of Apollo. As with recent comet studies, asteroid investigations may give us information about the origin of the Solar System, and perhaps tell us something about sources of early water and organic materials. This NASA Goddard animation offers a fine overview of the target and the overall mission.

But OSIRIS-REx is about more than the early Solar System. Recent scare stories have compelled NASA to state that a different asteroid, sometimes identified as 2012 TT5, will not impact our planet in September of this year. As Colin Johnston points out in Astronotes (the blog of Armagh Planetarium), 2012 TT5 will, on the 24th of September of this year, pass within 0.055 AU, or roughly 8.25 million kilometers of the Earth, a rather comfortable miss in anyone’s book. We’re talking about a distance twenty times further than the Moon is from the Earth. [NOTE: I originally mis-stated the kilometer equivalent of 0.055 AU, now fixed thanks to readers who spotted the mistake in the comments].

In other words, this asteroid poses no problem whatsoever when it passes by in September. Let me just quote the NASA news release briefly to get this out of the way:

“There is no scientific basis — not one shred of evidence — that an asteroid or any other celestial object will impact Earth on those dates,” said Paul Chodas, manager of NASA’s Near-Earth Object office at the Jet Propulsion Laboratory in Pasadena, California.

In fact, NASA’s Near-Earth Object Observations Program says there have been no asteroids or comets observed that would impact Earth anytime in the foreseeable future. All known Potentially Hazardous Asteroids have less than a 0.01% chance of impacting Earth in the next 100 years.

The longer-term picture is that assessing asteroids that could be a problem — astronomers call these Potentially Hazardous Asteroids, or PHAs — is an ongoing effort and a wise one. We know that asteroid impacts have had a role to play in the history of our planet, and it would be folly to ignore the potential. Fortunately, the OSIRIS-REx mission plays into that effort, because Bennu is an object with a chance (about 1 in 2500) of impacting the Earth late in the next century. Getting samples here will help us understand how to mitigate any future impact.


Image: An artist’s concept of NASA’s OSIRIS-REx asteroid-sample-return spacecraft arriving at the asteroid Bennu. Credit: NASA’s Goddard Space Flight Center Conceptual Image Lab.

An extremely dark object, Bennu absorbs most incoming sunlight and radiates it away as heat. This brings the so-called Yarkovsky effect into play, gradually changing the orbit of the asteroid over time. Clearly, understanding the asteroid’s trajectory involves anticipating what this tenuous effect can do. Edward Beshore (University of Arizona), who is deputy principal investigator for OSIRIS-REx, explains the mission’s role:

“We’ll get accurate measurements of the Yarkovsky effect on Bennu by precisely tracking OSIRIS-REx as it orbits the asteroid. In addition, the instrument suite the spacecraft is carrying is perfectly suited to measure all the things that contribute to the Yarkovsky effect, such as composition, energy transport through the surface, temperature, and Bennu’s topography. If astronomers someday identify an asteroid that presents a significant impact hazard to Earth, the first step will be to gather more information about that asteroid. Fortunately, the OSIRIS-REx mission will have given us the experience and tools needed to do the job.”

When Bennu was selected as the target in 2008, there were over 7000 known Near-Earth Objects (NEOs), of which fewer than 200 had orbits with the low eccentricity and inclination best suited for the mission. At 492 meters in diameter, Bennu is large enough to offer a stable target for the lander, with a carbon-rich composition believed to include the organic molecules, volatiles and amino acids that could be considered life’s precursors. Of the list of 7000, only 5 NEOs met all these criteria. Bennu was the final pick, and we’ll track OSIRIS-REx’s operations there with great interest. The spacecraft is to arrive at the asteroid in August of 2018.


Comments on this entry are closed.

  • Curt Wohleber August 25, 2015, 13:14

    Isn’t .055 AU something like 8 million km?

  • Bynaus August 25, 2015, 15:06

    Nice animation – with only minor artistic liberties taken… :) Note that 0.055 AU is NOT 150 million kilometers – its about 8.25 million kilometers. Still a huge distance in anyone’s book, as you write (more than 20x the distance between the Earth and the Moon).

  • Tom Mazanec August 25, 2015, 16:39

    The 150 million Km is the AU, not the 0.055 AU.
    Here’s hoping we can do repeats with the other four asteroids.

  • Paul Gilster August 25, 2015, 16:58

    Yipes, how did I miss that AU to kilometer conversion mistake? Now fixed and noted in the main text. Thanks, guys.

  • Hiro August 26, 2015, 2:08

    This “prediction” must have come from that sf novel Titan (Baxter), some serious reader perhaps.

  • J. Jason Wentworth August 26, 2015, 2:45

    This is a very timely article. The large population of NEAs (I often use the other term, “NEOs,” because some of these objects might actually be extinct comet nuclei) makes it prudent to characterize them regarding their chemical compositions *and* their physical states (which ones are solid rock, rubble piles, iron-nickel metal, dust-insulated dirty ice, stony-iron, chondritic, achondritic, and carbonaceous chondritic). Also:

    As well as sample return missions from selected asteroids, slow flyby or rendezvous/orbiter missions to provide overviews of the objects that could strike the Earth would be useful, simply because there are so many such objects that need to be examined. JAXA’s tiny (60 cm) PROCYON microspacecraft asteroid flyby probe (which was launched as a “hitch-hiker” payload with their larger Hayabusa 2 asteroid sample return probe; unfortunately, PROCYON’s ion engine could not be started, making the planned flyby of its own target asteroid impossible) is a type of spacecraft that could be launched in considerable numbers (several could be launched on one rocket), to investigate the potentially hazardous NEOs. Hopefully JAXA will fly more probes of this design (I’m going to suggest this to them).

  • ljk August 26, 2015, 11:43

    If it isn’t yet another bunch of nonsense (deliberate or otherwise) about a PHA (Potentially Hazardous Asteroid) threatening Earth, it will be an alien spaceship following a comet like with Hale-Bopp and Heaven’s Gate in 1997. Of course it will only be a very prominent comet that makes the mainstream news, never one of the lesser comets that only catch an astronomer’s attention.

    Tyson tried to show how ancient and wrong humanity’s negative and superstitious reactions to comets were in episode 3 of last year’s new Cosmos series, but of course it is like throwing a bucket of sand on a house fire.


  • Hop David August 26, 2015, 11:46

    Existing search programs are good for finding potential dino killers (Chicxulub sized rocks). But not potential city killers (Tunguska or Chelyabinsk sized rocks). And the latter is thousands, perhaps millions of times more likely.

    I’m very pleased that the OSIRIS REx mission is moving forward, but I’d like to see a lot more going on with NEA exploration. Realizing Planetary Resource’s goal of finding many small NEAs would also give us a better inventory of potential city killers.

    I would like to see robust SEP rock retrieval vehicles as suggested in the Keck Report and the Asteroid Redirect Mission. Such a vehicle may be ineffective for deflecting dino-killers but might well be up to deflecting a city killer.

    I don’t see governments commiting the needed funds for space settlement. The only way we’ll see steadily growing space infrastructure is if said infrastucture generates revenue streams.

    Government-private partnerships have established transportation and communication infrastructure in the past. It can do so again. I would like to see more NASA investment in the efforts of Deep Space Industries and Planetary Resources.

    But at least OSIRIS REx is a step in the right direction.

  • ljk August 26, 2015, 11:48

    A TPS blog item about PROCYON and its unfortunate failure to reach a planetoid here:


    Hey at least the Japanese are trying. I am saddened that more hubbub was not made out of the fact that they put a solar sail named IKAROS into solar orbit, where it flew past Venus at a distance of just 80,000 kilometers in late 2010:


  • Alex Tolley August 26, 2015, 12:05

    @J Jason Wentworth – a nice article on interplanetary cubesats CubeSats to Mars and beyond

    Cheap cubesats being used a pathfinders before the big probes go to their targets. We’ve talked about this before, and I think there is a lot of merit in flying small probes to explore and collect data, either alone or in swarms, perhaps imbued with swarm intelligence as well. Common platforms and mass production will drive down costs and open up the rate of scientific data collection. Landers and penetrators on Ceres could be a suitable mission.

  • spaceman August 26, 2015, 12:15

    Wow, sometimes I find myself having to take a step back and just be amazed that we are able to map an asteroid from its orbit! After all, it has only been for a small sliver of time in the history of our civilization when such a feat could be accomplished.

  • J. Jason Wentworth August 28, 2015, 6:10

    Thank you, Alex and ljk, for the links!

    I’m afraid that, absent a relatively quick ramp-up of asteroid mining (to “mine away” PHAs), governments will be the only entities able to protect Earth from them.

    But governments won’t commit really useful (I’m not saying OSIRIS REx, Hayabusa 2, and PROCYON *aren’t* useful; they are, but they’re like using a spoon to dig an escape tunnel) levels of resources to planetary defense until we have either [1] a “city-buster” object impact on or explode over a city with great loss of life, or [2] perhaps a very scary ‘close call’ with something far larger than the Chelyabinsk object. Until then, their reflexive refrain will be, “Yeah, we know that we’ve been hit before and will be hit again with a really big one, but it won’t be until long after we’re all dead, so we’re not going to spend money on it.”

  • ljk August 28, 2015, 9:48

    The B612 Foundation is trying to solve that cosmic issue:


  • J. Jason Wentworth August 29, 2015, 8:05

    Indeed, ljk, the B612 folks (and their partner in developing the Sentinel intra-terrestrial solar-orbiting telescope spacecraft and mission, Ball Aerospace) may one day prove to be “the unsung heroes who saved the world.” Planetary Resources and/or Deep Space Industries, who are working on their own space telescopes to find nearby asteroids to mine, might also discover one or more PHAs during the course of their observations. Plus:

    The B612 Foundation’s asteroid deflection demonstration mission scares many people (likely needlessly, I think, but once the public decides that something is bad and dangerous–RTGs on deep space probes are another example of such hysteria–the fear-generated socio-political headwinds are hard to overcome). But if they instead tried raising Deimos’ orbit around Mars (the “worst” thing that could happen would be a tiny lengthening of its orbital period; only astronomy textbook publishers might get peeved at that :-) ), that could demonstrate the asteroid deflection technology without triggering “China Syndrome”-type protests.

  • J. Jason Wentworth August 29, 2015, 8:57

    ljk wrote:

    A TPS blog item about PROCYON and its unfortunate failure to reach a planetoid here:


    Hey at least the Japanese are trying. I am saddened that more hubbub was not made out of the fact that they put a solar sail named IKAROS into solar orbit, where it flew past Venus at a distance of just 80,000 kilometers in late 2010:


    They’re still operating the otherwise (besides its apparently short-circuited ion engine) fully-functional PROCYON asteroid mini-probe, which is heartening (JAXA’s pre-merger space science agency, ISAS, seemed to give up on ailing probes more readily). Apparently it will fly by Earth even without an ion drive maneuver, so it might pass within useful distance of other asteroids in the future. Short-period comet encounters are also possible, as some of the solar-orbiting Pioneer 6 – 9 probes also moved within useful range of such comets (including Halley’s Comet); in such cases, “the targets come to the spacecraft.” Also:

    I too am disappointed that IKAROS’ accomplishments are so little-heralded in the West. Just as Mariner 2 failed to capture the imagination of the American public in 1962, despite being the first successful mission to another planet (it carried no camera to take close-up pictures of Venus; not until Mariner 10 in 1974 [after the camera-less 1967 Mariner 5 mission] did a U.S. probe image Venus up close, and its TV cameras were onboard because Mercury was its ultimate destination), the relative paucity of images from IKAROS (plus their small size, from the Venus flyby) might be part of why this pioneering mission is little-known here. In addition:

    IKAROS didn’t deploy its solar sail very close to Earth, so it didn’t dazzle viewers on the ground. Plus–and I say this with sadness, not to “pump myself up”–many of my fellow Americans just don’t grasp the significance of what IKAROS did, and what it can lead to. To many of them, if they’re aware of IKAROS at all, it’s just a strange, obscure thing that only “nerds” are interested in, and besides, it was built and launched by foreigners (“If it was worth doing, *WE* would have done it first…”). Those of us who read “Centauri Dreams” and follow space flight and astronomy developments aren’t as numerous as we may feel here. But:

    IKAROS is apparently still operating (the last I heard, the sail’s “variable albedo” LCD steering panels weren’t being cycled properly, but the vehicle was otherwise functioning well), and hopefully its Venus orbiter “launch companion” will successfully enter circum-Cytherean orbit when JAXA tries it again, using the orbiter’s smaller thrusters this time.

  • ljk August 31, 2015, 8:52

    Whoever controls the planetoids (and the comets) control the Sol system.

  • Michael August 31, 2015, 15:42

    @ljk August 31, 2015 at 8:52

    ‘Whoever controls the planetoids (and the comets) control the Sol system.’

    I would have thought control Jupiter magnetic field and its moons materials and you have access to the huge energy storage in its field and a lot of building material. Jupiter’s magnetic field is 10 to 20 thousand times larger than Earths which is around 10 to 20 terawatt to generate. Then you control the solar system and an energy source to propel craft to the stars.

  • ljk September 1, 2015, 14:36

    Yes the Jupiter system is a great place in terms of resources and energy, but keep in mind you also have some seriously nasty radiation belts to contend with, along with Jupiter’s very deep gravitational well.

    Mining planetoids and comets are much easier by comparison and far more plentiful. Millions of raw chunks of minerals with relatively low gravity fields all over the Sol system just waiting to be utilized.