Asteroid comparison chart

By Phil Plait | July 20, 2010 7:22 am

Emily Lakdawalla — scientist, blogger, and all around cool chick — has just posted a totally awesome scale diagram comparing every asteroid and comet visited by spacecraft. It features pictures of all the rocks, each of which she has carefully resized so you can see just how big they are relative to each other:

emily_asteroids_comets

Whoa. Look how big Lutetia, just visited by Rosetta, is compared to everything else! And yet, at 130 km across, it’s a dot compared to our Moon. In fact, you could smash together all the known asteroids in the main belt between Mars and Jupiter and they’d be far smaller than our rocky satellite.

Still, small doesn’t mean "uninteresting". These rocks in Emily’s diagram are all fascinating beasts, and the more we learn about them the more compelling they become. And there’s more to come, with the Dawn mission about to see the big asteroids Vesta and Ceres up close… and go read Emily’s blog about this to see how they’d fit on the diagram (hint, they don’t, and by a long shot). You’ll also find a much larger version of the diagram there, and you really, really should look at it. Wow.

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (35)

  1. gopher65

    IIRC all the rocks in the belt between Jupiter and Mars have a mass of only 4% of that of Earth’s moon (which itself is only what, 1% of Earth’s mass?). That sure puts that “failed planet” garbage in perspective.

  2. Messier Tidy Upper

    Wow indeed! I knew Lutetia was the largest asteroid we’d yet visited but I didn’t realise by quite how much! Or quite how tiny Itokawa is – its almost too small to spot on this scale. Can’t wait for Ceres and Vesta to be added to that chart. Dawn is getting there 2014 right? :-)

    Thankyou Emily & the BA for bringing us this. :-)

  3. Elmar_M

    Interesting. I always thought it was a planet…
    That really is not a whole lot of mass. I thought it was much more.

  4. Messier Tidy Upper

    @ ^ Elmar_M : Well it is a minor planet! Actually they all are. ;-)

  5. Awwwww, the little ones….! I just want to give ‘em a big ol’ hug!

    Then pulverize the lot of ‘em for my O’Neill colony at L-5.

  6. Look at the shape of Halley. How long before it splits in two?

  7. Nonsense Alert:
    OK – I’ve decided that Ceres is really a “death star” space ship. Hanging out there “watching” us. I’m going to develop this idea into a cult and call it “Stupidscientology”. Which I think I can get away with cause its not a name that Scientology embraces, so we could be distinctive. Of course I’m not married to the name, I could go another way.

    If you are interested in getting in on the ground floor of my cult development, let me know. If we work it, we will have 5 years of really good cultiness – ya know until Dawn lands on it and ruins it for us.

  8. PeterG

    Just look at how small Itokawa is, Hayabusa really did an incredible job.
    (congrats for this blog, really love it)

  9. I’d like to see Phobos and Deimos (moons of Mars) on this scale. Aren’t they probably captured asteroids?

  10. Are any more results in yet from the Lutetia flyby? It’s the first M-class asteroid visited by a spacecraft, and it has a density of 5.5, strongly implying a metal interior, but it sure looks like all the rest (except for size). Is it a chunk of metal covered by rock, or what?

  11. Rick W.

    I’m with you Non-Believer. We could call ourselves “Knot Ceres Us”. Not a perfect “not serious”, but, we’re going to be wackos anyway.

  12. Non-Believer:

    OK – I’ve decided that Ceres is really a “death star” space ship. Hanging out there “watching” us.

    Sorry, but that job has already been taken by Mimas.

    (Yes, the tabloids actually said stuff like that back when Voyager sent back those first images back in 1980. Front page stuff, with photos, so it must be true.)

  13. Anne Verbiscer

    @ Phil K:

    Here you go (at least for Phobos):
    http://www.unmannedspaceflight.com/index.php?act=attach&type=post&id=22104

    Also to be noted on Emily’s poster, she took the time to orient each body so they all have the same illumination. Nicely done.

  14. magetoo

    Holy moley, the large version image is absolutely gorgeous. I’m almost tempted to try the gigantonormous one.

  15. Messier Tidy Upper

    I wonder if they’ll update this gravity well comparison :

    http://xkcd.com/681_large/

    to include all these asteroids too? After all its got Phobos & Deimos already and they’re about the same size – or are they? ;-)

  16. Jamey

    I was curious about the cities in the asteroid belt idea, and wanted to get an idea of the scale, so I checked – Guam is about half-way in size between Eros and Ida – except that Guam is a *surface*, and the asteroids are volumes! They’re *HUGE*! We really need to work on capture of an Earth-grazer, to give us a *REAL* space station to work from!

    Does anyone know if someone’s done a list of known Earth-grazing objects, and windows for minimum delta-v to capture them? Even something 100 meters or so would give us significantly more living space than the ISS – and a more solid base, perhaps.

  17. Messier Tidy Upper

    @5. kuhnigget Says:

    Awwwww, the little ones….! I just want to give ‘em a big ol’ hug! Then pulverize the lot of ‘em for my O’Neill colony at L-5.

    Well you could do that I guess but turning them into generation ship asteroid arks and sending them off to the nearer stars sounds like a
    better plan to me. :-)

    @6. Ken B Says:

    Look at the shape of Halley. How long before it splits in two?

    Hopefully NOT until after its been back past us again – we’ll miss it when it goes. :-(

    2061 or 2063 I think is the next time around.

  18. @Rick W. Excellent Name. I endorse it.
    @ Ken B. Thanks for the heads up. I will contact the tabloids immediately so we can start this ball rolling with a front page article. I assume I can just email them the info – they don’t really need evidence or anything. If they do, we may need to recruit some conspiracy engineers. They’re really good at that stuff.

    Hey on a side note – Did you guys see the new Moon Hoax cartoon by Darryl Cunningham. Very Nice. http://darryl-cunningham.blogspot.com/2010/07/moon-hoax.html

  19. andy

    The comparison to 4 Vesta and 1 Ceres is quite impressive. 4 Vesta in particular should definitely be an interesting visit: it is thought to be differentiated, and there’s that huge crater that may provide a look into the interior.

  20. Torbjörn Larsson, OM

    Lutetia, sounds like someone’s great granny.

    That sure puts that “failed planet” garbage in perspective.

    Or perhaps commute it, since it is remains of the protoplanetary nebula, only further processed “in another direction”.

    AFAIU exoplanet statistics seem to put planets densely, i.e. they may be likely to be as packed as they can go without disturbing each other. Granted, that is after migration (due to said disturbances or what not), but another result could be that asteroid belts are scarce and likely to be narrow, and in some sense indicating failure in the full “accretion and packing” process.

    Aren’t they probably captured asteroids?

    IIRC it is fairly certain Deimos is; while it could be a toss up whether Phobos is that, or is something like our moon, collected impactor ejecta. Phobos could be a “rubble pile main belt asteroid”, but its composition reminds of Mars AFAIU. Samples needed!

    Are any more results in yet from the Lutetia flyby?

    I would like to know too, especially the magnetometer results: if it’s a remnant of a larger and differentiated object, Lutetia could have a remaining magnetic field!

    The latest Planetary Society Planetary Radio show had the project leader describe how currently there’s a lot of image processing going on in parallel with the rest, and apparently they show interesting stuff.

  21. MoonShark

    In fact, you could smash together all the known asteroids in the main belt between Mars and Jupiter and they’d be far smaller than our rocky satellite.

    Really? I had no idea. I thought Ceres alone was like 1/3 the size of Luna. But Wikipedia says it’s almost a 100-fold difference in mass. Whoops. Guess I should never assume! Thanks Phil.

  22. amphiox

    I thought Ceres alone was like 1/3 the size of Luna

    That’s diameter (more closely about 1/3.5). So if you’re talking about volume, the ratio gets cubed. Then you have to factor in density….

  23. @kuhnigget: Just one? I bet you could make like a million colonies out of Lutetia alone, enough to support a population of billions.

  24. Attack of the Killer Potatoes !!!

  25. Grimbold

    Where’s 132524 APL? Visited by New Horizons in ’06.

  26. @ Arik Rice:

    Just one? I bet you could make like a million colonies out of Lutetia alone, enough to support a population of billions.

    Why off Earth would I want a population of billions in my space colony???!!

    Me, the members of the Japanese football team, someone who knows how to make Mountain Dew, a couple dozen Welsh Corgis, and that’s it!

  27. locke

    Factoid: the ORIGINAL mass of the planetisimals in the asteroid belt may have been similar to that of the Earth. Of course, the great majority of that mass has been lost thru collisions with the major planets and ejections from the solar system.

  28. Thanks, Phil, for the glowing writeup! To those who asked about Phobos, there’s an earlier version of the montage, lacking Lutetia but being in color, here: http://www.cafepress.com/planetaryshop.349861325 I was going to wait to update that until after the Hartley 2 flyby later this year. Phobos and Deimos are, very roughly, Eros- and Halley-sized, respectively, but rounder. Grimbold, the images that New Horizons got of 132524 APL were only a couple of pixels; they were enough to determine the color and approximate size but no surface detail could be seen. The encounter was pretty distant as asteroid encounters go, about 100,000 kilometers — a “Voyager-class” flyby of an object far smaller than those Voyager was able to study with its cameras. So I chose not to include it. See here for more: http://www.planetary.org/explore/topics/new_horizons/nh_071906.html

  29. By the way, this is Lutetia next to our Moon. Just a rough estimate.
    http://gamedesignreviews.com/wp-content/uploads/2010/07

  30. truthspeaker

    Phil K Says:
    July 20th, 2010 at 9:31 am

    Are any more results in yet from the Lutetia flyby? It’s the first M-class asteroid visited by a spacecraft, and it has a density of 5.5, strongly implying a metal interior, but it sure looks like all the rest (except for size).

    I don’t think those are mutually exclusive. Iron ore looks pretty much like rock. Well, it is rock.

  31. Pi-needles

    @^ truthspeaker Says: Iron ore rock? ;-)

  32. Gary Ansorge

    32. Pi-needles

    “Iron ore rock?

    Now, THAT’S some real “Heavy Metal”.

    I prefer Rhythm and Blues.

    Does anyone here know the distance between Vesta and Ceres?

    Gary 7

  33. Phil K Says:
    July 20th, 2010 at 9:24 am
    I’d like to see Phobos and Deimos (moons of Mars) on this scale. Aren’t they probably captured asteroids?

    Some infromation for you. Please follow links:

    Phobos: http://aleksey-galan.blogspot.com/2010/03/phobos.html

    At this very difficult to believe that two different satellite captured rotate in one plane, even if we imagine that the fact that their orbits by the planet’s equator – just a coincidence.
    Most scientists are still inclined to believe that Phobos and Deimos – an asteroid, trapped in the gravitational capture of Mars. However, this theory, according to the University of Virginia Professor Fred Singer, is in conflict with the laws of physics can not explain why the two satellites moving around the planet for nearly circular and equatorial orbits. Periods of rotation around the axis of each of the satellites coincides with the period of revolution around Mars.

    Low density and the internal cavity of Phobos and asteroids:
    http://aleksey-galan.blogspot.com/2010/03/low-density-and-internal-cavity-of.html

    The density of Phobos – less than 2 g/cm3. Planetologists explain it loose or porous material, forming its breed.
    The average density of Phobos is 1,90 ± 0,08 g/cm3. The density of Phobos, defined according to the navigational measurements “Viking”, which were obtained in less favorable ballistic conditions was 2,2 ± 0,2 g / cm 3 (Williams et al., 1988).
    A tiny satellite of Mars – Phobos – has the same powerful magnetic field, like Earth.

    Artifacts on Phobos: http://aleksey-galan.blogspot.com/2010/05/artifacts-on-phobos.html
    What we see here?
    What could be the brightest object in the crater?
    This object has a long shadow. It is metalic?

  34. Rectangular Structure on Eros
    http://near.jhuapl.edu/iod/20000503/
    This image of Eros, taken from the NEAR Shoemaker spacecraft on May 1, 2000, is among the first to be returned from “low orbit.”

    Square craters on the Moon
    http://aleksey-galan.blogspot.com/2010/03/square-craters-on-moon.html

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