Stardust snaps close-ups of a second-hand comet!

By Phil Plait | February 15, 2011 2:33 pm

A philosopher once asked, "Are we human because we gaze at the stars, or do we gaze at them because we are human?" Pointless, really… "Do the stars gaze back?" Now that’s a question.
-Narrator, "Stardust"

Late last night, the NASA mission Stardust flew within 178 km (110 miles) of the nucleus of the comet Tempel 1, seeing it up close for the first time since July 2005! Here’s one of the better images from closest approach:

[Click to embiggen.]

Wow! The whole flyby sequence has been posted on NASA’s Stardust site (and Emily Lakdawalla at The Planetary Society blog has created a nifty animation of it too).

Ian O’Neill, from Discovery News, posted a nice animation of it as well on YouTube:

To give you an idea of what you’re seeing here, the comet is roughly 7.6 x 4.9 kilometers (4.7 x 3.0 miles) in size.

So, why did NASA fly Stardust past this comet? Ah, set the way-back machine for 5.5 years ago…

In July 2005, NASA’s Deep Impact space probe flew past the comet Tempel 1. As it did, it slammed an 370 kilogram (800 pound) block of copper into the comet at a speed of 10.2 km/sec (6.3 miles per second). The purpose was to create a crater on the surface and excavate deeper material, allowing scientists to see what lay beneath. When the impactor hit, the energy released was equivalent to nearly 5 tons of TNT exploding! And while some amazing images were returned, the expanding cloud of debris blocked the best views, and so it wasn’t possible to get all the data they wanted.

The Stardust probe, meanwhile, was originally launched to collect samples from the comet Wild-2 and return them to Earth using an ejectable return container. The main probe sailed on, and engineers repurposed it to swing by Tempel 1 to see if any new images could be taken. And now, nearly six years later, the renamed Stardust-NeXT (Stardust-New Exploration of Tempel) mission has succeeded!

The whole point here was to see the impact crater from 2005, and Stardust was able to do that. It’s difficult to see in these images here, but Pete Schultz, an impact specialist with the mission, said the crater is about 150 meters across and has a central peak, indicating material fell back to the comet. The crater wasn’t as obvious as expected, but is about the right size given the impactor speed, mass, and angle of impact.

Here’s a comparison of one of the new Stardust images with an image taken from Deep Impact in 2005:

On the right is an image from Stardust near closest approach, and on the left is one from Deep Impact, which I rotated to match up the orientation. The angle of observation was different for the two spacecraft but you can see some of the same features. For example, on the DI image you can see two large craters on the left, and those are also in the Stardust picture fairly well centered. It so happens that the impactor from DI hit between those two craters, very close to the one on the left. As I mentioned, the new crater is extremely difficult to see — during the press conference, I couldn’t see it even when the location was pointed out!

Comets don’t have weather like planets do — no atmosphere! — but their icy surfaces get modified as they approach and recede from the heat of the Sun. Other Stardust images do show some changes to the comet’s surface! As the scientists get more of a chance to compare before-and-after shots, they’ll be able to see even better how this tiny world has changed since we visited it last.

Image credit: NASA/JPL-Caltech/Cornell; NASA/JPL-Caltech/UMD

Related posts:

Deep Impact: Bang! Success!
Deep Impact interview with Brian Cox
Amazing close-ups of comet Hartley-2
A comet creates its own snowstorm
Dust from the stars

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (39)

  1. Cool. I hope they’ll post better images of the impact site. Or even just rotated/scaled/etc images that match the 2005 images with the new ones.

  2. Stark

    We really are some clever little bits of carbon aren’t we? Hurtling a small device at over 10km per second halfway across the solar system to come within spitting distance of a 7km long chunk of rock and ice moving at very high speed itself… and do it not once but twice with the same vehicle. Add to that being able to take highly detailed photos of the event and send them back across the blackness of space to our tiny little ball of water and dirt…. Simply jaw dropping.

    Now, if we can just get a large enough sample of that ice back here… I’m in the mood for a Comet Icee! 😉

  3. Robert

    That picture, and the fact that you can’t even see the crater, makes all those fears about changing the comet’s trajectory seem really silly right about now. Ah, hindsight (and math, and physics…)

  4. Can’t help noticing that the background stars don’t show up in these images. Do the Moon-hoaxers think these are fake too?

  5. Was Stardust initially designed to do more science after it had ejected the samples or was this repurposing a complete after thought?

  6. Dave

    The impact site is between the craters if you say so. Not much to see with the unaided eye, but cool nontheless. The deep impact projectile probably felt like a bug hitting the windshield to the comet.

  7. Donnie B.

    Doesn’t look very much like that comet in Armageddon, does it? Must be fake!

  8. So cool, so tantalizing… but AAUGH the slideshow-vision makes me all *sadface* and want to see the flyby at 30 frames per second!

  9. Steven Spray

    The shutter speed is not delayed long enough for starlight to make an ‘imprint’ on the photo. But I’m sure those hoax’ins will have other BS up their sleeves!

  10. Alan D

    And still completely free of advertising and signage. How unusual!

    Maybe by the next visit.

    Clear skies, Alan

  11. Messier Tidy Upper

    Superluminous news – and images! Congratulations & thanks to all those involved. :-)

    Valentine’s encounter? (On the youtube animation by Ian O’Neill.)

    I thought the renamed name was Stardust-NeXT not Valentine! 😉

    Also I rather wish they wouldn’t do that renaming thing they seem to keep doing now. (Eg. Deep Impact -> EPOXI) What’s wrong with just calling it Stardust still & simply saying this is it’s extended mission instead? Minor gripe but still.

  12. Stardust Engineer

    @Daniel – the extended mission was a complete afterthought. It’s the little spacecraft that could.

  13. Johnny Davidson

    Is that Jimmy Hoffa?

  14. Messier Tidy Upper

    @ ^ Johnny Davidson : No, its Harold Holt! 😉

    (Wonder how many non-Aussies will get that one?)

    Also I rather wish they wouldn’t do that renaming thing they seem to keep doing now.

    Just adding I don’t mind the cases of honouring some of the great scientists like Carl Sagan :

    and Gene Shoemaker :

    with some appropriate renamings. Those are fine.

    As is the permanent name change for the Fermi gamma-ray space observatory :

    from GLAST or the Japanese changing Muses-C into Hayabusa once that was successfully launched. Those are apt & great too and were improvements on their original “working titles” in my view. I just don’t see the point or value in making up the new acronyms for the spaceprobe names for the extended missions. (Eg. EPOXI, Stardust-NexT.) It just seems to be unneccesary & potentially confusing.

  15. Jon

    “Comets don’t have weather like planets do — no atmosphere! — but their icy surfaces get modified as they approach and recede from the heat of the Sun.”

    And when every now and then pesky little monkeys throw bricks of copper at them… :)

  16. Second-hand comet dust used to be a real problem until they outlawed comets in the work place. We can all breathe easier now.

  17. Gary Ansorge

    That question, “Are we human because we gaze at the stars, or do we gaze at them because we are human?” requires we also ask “Are there any other critters on this planet that gaze at the stars?”

    We like to think that we’re unique but we apparently just have more of what many other critters have, plus an overweening, smug self satisfaction.

    In this case, some of that may be well deserved. Thank evolution for these opposable thumbs,,,

    Gary 7

  18. jennyxyzzy

    I was interested by the way the image of the comet jumps around in the video sequence. What causes that? Is it evidence of Stardust manoeuvering?

  19. Quiet Desperation

    Second hand? Is it for sale?

  20. @2. Stark: No, don’t you remember? We’re “ugly bags of mostly water”, not carbon.

  21. JK Finn

    Am I the only one that finds himself somewhat awestruck by the minor detail that these pictures are taken by two *separate* spacecraft?

    well, maybe it’s just me.

  22. Keith Bowden

    Hmph. “Second hand” is just marketing lingo for “used”. Never trust a used comet dealer…

  23. Harlequin

    After reading all the horrible political and international news today and having a rousing discussion on it that was just sad, I hit this article, and all of my responses were simply links of this post and “Its a picture of a f-ing comet”.

    These images are absolutely amazing and have reduced me to a child-like state of wonder and awe. Utterly amazing what we can do, and what the universe holds.

  24. Robert Gibson

    Why did they use copper? Wouldn’t steel or lead have been cheaper?

  25. Paul A.

    “[Click to embiggen.]”
    What, no “[Click to emtempelate]?”

    I’ve come to expect more from you.

  26. Joseph G

    @29 Robert: I was wondering that too.
    I would guess that it’s because copper is spectroscopically distinct from the stuff they expect to find in the comet, so it wouldn’t mess up their readings as they’re doing a spectral analysis of the plume of stuff coming away from the impact. I don’t know about lead, but iron is pretty common in some asteroids, so there’s a possibility that some was deposited in/on the comet, and steel contains carbon, so both are things you wouldn’t want to fire at a comet if you wanted to know exactly what its composition is.
    For all I know, it could be something completely different, though. Maybe copper is more ductile and they wanted the impactor to flatten out as it penetrates instead of fragmenting. Just guesses…


    RE: The use of copper for the projectile.

    According to NASA’s “Deep Impact — Mission to a Comet” website:

    The impactor spacecraft is composed mainly of copper, which is not expected to appear in data from a comet’s composition.

    So, Joseph G, you can now give yourself a pat on the back for guessing correctly. 😉

  28. Messier Tidy Upper

    @26. JK Finn :

    Am I the only one that finds himself somewhat awestruck by the minor detail that these pictures are taken by two *separate* spacecraft?
    …well, maybe it’s just me.

    Not just you – it’s me as well & I suspect a great many others too! 😉 :-)

    PS. Well guessed and worked out Joseph G. (#31.) – Good thinking. :-)

  29. Joseph G

    @32 IVAN: Woohoo!!! I are so smart! Ess Em Are Tee!
    *runs over to machine, pushes button*

    AGH!! Iv-a-n-n-n-n-n! St-op th-is cr-az-y th-ing!!!

  30. Chris L.

    Anyone have any ideal what is causing the layering?

  31. Akash

    but how the copper body is impacted on the comet, since the comet doesn’t have that much gravity as earth??


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