… in the sky, with diamonds

By Phil Plait | September 6, 2008 11:01 am

If Godzilla got engaged, then this is the rock he’d have to buy his belle:

Asteroid Steins, as seen by Rosetta

That’s asteroid 2867 Steins, as seen by the European Rosetta spacecraft when it passed only 800 kilometers away on Friday. It’s literally a diamond in the rough! Man, that’s weird. Asteroids of this size range (Steins is about 5 kilometers (3 miles) across) can theoretically be pretty much any shape; the gravity of an object that size isn’t strong enough to morph the rock into a sphere. Moreover, countless collisions with other asteroids tend to make them roundish, not jagged, but most of the ones we see are either roughly spherical due to random collisions, or potato-shaped (astronomers fondly call them "spuds").

But a diamond shape? Wow. And it’s not an illusion due to perspective; this is a real 3-D shape. Do you have a pair of red/green glasses*? Then take a look at this:

Anaglyph of Steins

If you do have the glasses, you can see the diamond shape extends all the way around at least the visible half of Steins. And since Rosetta actually physically passed the asteroid and took pictures as it went by, more than half of Steins was mapped. The shape appears to hold up. It really is shaped like a diamond.

And it gets weirder. Steins has a ginormous crater on it, spanning 1.5 km (1 mile) of its surface. That’s pretty big, and the impact that created it must have been impressive. In general, if Steins is a solid chunk of rock, an impact that large could have shattered it, or at least infused it with cracks. That makes me wonder if Steins isn’t solid, but is instead a rubble pile; a pile of loose chunks held together by its own weak gravity.

Some asteroids have very low density, and astronomers think that these used to be solid bodies, but after hundreds of low-speed collisions with other asteroids they shatter in place, resembling a bag of glass. A lot of the volume of such an asteroid is then empty space, lowering its density.

A pile like that can take a much larger impact without breaking apart than a solid body; imagine dropping a hammer on a bag of sand versus a glass plate. Is Steins like that? I don’t know.

Crater chain on asteroid SteinsAnd there’s more weirdness: it has a crater chain! You can see a linear series of six or seven small craters in the image on the left. Many bodies in the solar system have such chains, and the irony is that they may be caused by objects like Steins itself.

A rubble pile isn’t held together very strongly because of the object’s low gravity. If an asteroid like that gets near a much more massive object, like say Jupiter, the tides from the bigger object can pull the smaller one apart. Instead of one pile of rocks, you get a long chain of smaller rocks. That happened to comet Shoemaker-Levy 9 shortly before it impacted Jupiter in 1994, so we know for a fact (I almost wrote "rock solid" fact) that this happens.

If a chain of rocks hits another body, it can leave a linear series of craters just like what we see on Steins. So perhaps some other rubble pile got torn apart millennia before, then Steins got in its way. It’s hard to say in these low-res images, but I’d bet it’s something close to that.

Asteroids are fascinating. Every single one we see is weird, shattering some of our preconceived notions of what’s what in the solar system. That amazes me; we understand how stars are born and die, how distant galaxies collide, and even have a decent handle on how the Universe itself formed. But here we have rocks almost literally in our back yard, and they are capable of surprising us.

Science! I love this stuff!


*What? You don’t? Then how do you expect to see any void stuff?


Comments (42)

  1. Cameron

    Only 800 k away? That sounds kind of close. Do many asteroids pass at that distance?

  2. COOL! Click on my name to see the flyby.

  3. Nathan Myers

    That’s not ironic at all.

  4. madge

    Beatcha to it BA! (see comment on previous post) Rosetta Rocks (quite literally)

  5. madge

    @ Cameron
    Rosetta was only 800 km away from Stein. Stein is way further away from Earth than that!

  6. Sili

    Is 800 km close enough that Steins (“Stones” – how appropriate) affects Rosetta’s path so that we can estimate the mass?

  7. @Cameron,
    I think he means the Rosetta spacecraft passed within 800 km of the asteroid, not that the asteroid came within 800 km of Earth. :)

  8. pumpkinpie

    Raise your hand if you actually had a pair of red/blue glasses within reach! (hand raised)

  9. Greg in Austin


    The Rosetta spacecraft was 800km from the asteroid, but they are both “At a distance of about 2.41 AU (360 million kilometres) from our planet,” according to the ESA – Rosetta website.

    Not really close.


  10. Andy

    “Science! I love this stuff!”

    Yeah. It’s cool. You should post about it more…

    (and maybe less about encounters with internet semi-celebs)

  11. Chip

    Here’s a simple map giving an impression of where 2867 Steins is within the Solar System.

  12. scotth

    Buying Shrek 3-d has finally paid off.

    Very cool!

  13. Supernova

    they shatter in place, resembling a bag of glass.

    This made me laugh because it reminded me of that classic SNL “Consumer Probe” skit with Candice Bergen and Dan Aykroyd.

    Consumer Reporter: So, you don’t feel that this product is dangerous?

    Irwin Mainway: No! Look, we put a label on every bag that says, “Kid! Be careful – broken glass!” I mean, we sell a lot of products in the “Bag O'” line.. like Bag O’ Glass, Bag O’ Nails, Bag O’ Bugs, Bag O’ Vipers, Bag O’ Sulfuric Acid. They’re decent toys, you know what I mean?

    Also: I told my freshman seminar students about the terrestrial crater chain recently discovered by an amateur astronomer using Google Earth, and they thought it was pretty cool. I’m definitely recommending the BABlog to them!

  14. Jeffersonian

    Cool rock. Cool description. Way.

  15. kuhnigget

    “The shape appears to hold up. It really is shaped like a diamond.”

    Naaah….it’s the fossil remnant of one of those cool, floating world things Roger Dean used to paint for Yes album covers.


  16. Radwaste

    Hey – don’t forget the other asteroid coolness Phil has posted!

  17. amphiox

    Egads. This asteroid is so complex, and interesting (far more so than a certain human being of the same name, for instance), it must have been designed.

  18. Wow! So, so cool. Can’t wait to show my kid – I think we have our Nightmare Before Xmas glasses here somewhere…

  19. Nathan Myers

    Also, there really are (literally!) diamonds-in-the-rough in space, miles across, but that one is not “literally” a diamond, rough or otherwise. Furthermore, it’s not even shaped like a rough diamond, which doesn’t have any particular shape. Rough diamonds look like ordinary rocks.

    What you can say about this is it’s shaped a lot like a cut diamond, which is more impressive than a “diamond in the rough”.

  20. Nathan Myers

    Finally, to be impressed that an asteroid has a cut-diamond shape is perilously close to being impressed with pareidolia.

  21. *sigh* I knew someone would make the above anal comment as soon as I read the ‘diamond in the rough’ bit. It’s just a play on words, that’s a bit erroneous if taken literally, get over it.
    And it’s not like he’s seeing the diamond shape and saying ‘all hail the diamond god’… the comment about the diamond shape isn’t based on a random coniguration made significant by brain-fiddling… he clearly states it’s not a usual shape for an asteriod, and therefore likely to be significant for non-iconographic reasons (but interesting none the less, just like a grape shaped like mary is interesting if you don’t go religious all over it and know what you’re seeing).

  22. Davidlpf


  23. kuhnigget

    Attention all BA commenters:

    Per the new anti-metaphor guidelines, no language shall ever be introduced suggesting any object looks, smells, feels, tastes, or sounds like any other object in the universe, unless both objects absolutely look, smell, feel, taste and sound exactly alike.

    This does not apply to anything made of plasma, because…oh, just because!

  24. Davidlpf

    Oh another new rule nothing shall be mentioned as ironic.:-)

  25. Mark Hansen

    BA, is it possible that Rosetta approached the asteroid upside-down? Because if you see the video that IVAN3MAN linked to, it looks a whole lot like Rosetta is flying by one of Gerry Anderson’s creations.

    And before you comment Nathan, no, it’s not exactly identical. You need to use your imagination and a little less pedantry.

  26. Andy: nope. And there’s more to come.

  27. Hmm

    Now I want to know what’d happen if this thing were solid diamond and it hit us.

    Because that’d either be really awesome or really sucky.

  28. Nathan Myers

    I’d be satisfied if only ironies were called ironic.

  29. Todd W.

    [pedantry]Irony: an outcome of events contrary to what was, or might have been, expected

    Many objects in the universe have crater chains possibly caused by objects like Steins. Steins also has, unexpectedly, a crater chain. [/pedantry]

  30. Gary Ansorge

    Oh, would that be Lucy, in the sky, with diamonds?

    Sorry. I just couldn’t resist,,,

    GAry 7

  31. Nathan Myers

    Todd W: It is far from unexpected for Steins, one of those “many objects in the universe” to have a crater chain. There are lots of other things it might be, such as “appropriate”.
    “Ironic” is a useful word that will remain useful only as long as it actually means something.

  32. wfr

    As an alternative to the bag-of-glass explanation for the large crater, isn’t it possible that the large crater was formed on a large planetoid in the distant past, and then the planetoid was broken up by a later collision?

  33. Melusine

    The crater chain is cool, especially imagining what seeing the impacts would have been like.

    Nathan Myers said: Finally, to be impressed that an asteroid has a cut-diamond shape is perilously close to being impressed with pareidolia.

    There’s nothing wrong with pareidolia and pattern recognition. Astronomers name nebulas after familiar objects. It’s only bad when you think it has meaning apart from coincidence and patterns that that result from similar physical events.

  34. That looks an awful lot like the emblem on Superman’s chest.

    I’m a little fuzzy on this, but at the end of Superman II didn’t Supes use a peel-off version of his emblem to re-trap the Kryptonian villains in the Phantom Zone? And then send them spinning off into space again? Where they would be safely trapped, as long as their new prison didn’t get a corner whacked off by something? Which would be really, really unlikely in the short-term?


  35. Didn’t Arthur C. Clarke surmise that the centre of Jupiter is a large earth sized diamond?

  36. Yep, Shane, in Clarke’s novels ‘Space Odyssey 2010’ & ‘2061’ both featured the (hypothetical) Jovian diamond core (or fragments therof) .. & the Lucy in the Sky with Drugs ..er ..Diamonds line.

    THX Bad Astronomer I’ve ben dying (METAPHOR .OK!) to hear how theRosetta- Steins encounter went & glad itwasn’t too close leaving Rosetta as astain onSteins! 😉

    Great to hear this news and that its gone so well – there’s been nothing in the South Aussie papers or TV news on this but I knew you wouldn’t let me down! 😀 8)

  37. CORRECTION for typos , spacing etc .. Coz Icasn’t @#@$$@#!!!%#@@!#@ ediut here. :-(


    StevoR Says:
    September 8th, 2008 at 1:16 am
    Yep, Shane, Arthur C. Clarke’s novels ‘Space Odyssey 2010′ & ‘2061′ both featured the (hypothetical) Jovian diamond core (or fragments thereof landning onEuropa!) .. & the “Lucy in the Sky with Drugs ..er ..Diamonds” line.

    THX Bad Astronomer I’ve been dying (A METAPHOR – OK!) to hear how the Rosetta Steins encounter went & glad it wasn’t too close leaving Rosetta as a stain on Steins!

    Great to hear this news and that its gone so well – there’s been nothing in the South Aussie papers or TV news on this but I knew you wouldn’t let me down! 😀 8)

  38. Nentuaby

    Figurative speech is the soul of artistic English writing. Would people, however, for the love of GOD PLEASE STOP SAYING “literally [figurative descriptor]”. That is exactly wrong.

    I thought you were talking, as you stated, about a whacking great carbon crystal.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar