Dawn approaches

By Phil Plait | July 14, 2011 10:30 am

The spacecraft Dawn is now just one day away from entering orbit around the asteroid Vesta, the second-largest in the main belt between Mars and Jupiter. On July 9th, it snapped this photo of the rock, from just over 40,000 km (24,000 miles) away:

As far as I can tell, this is the highest resolution image of Vesta ever taken! Vesta is a slightly flattened mildly-lumpy spheroid with a diameter of about 530 km (260 miles), and you can see it’s peppered with impact craters, as expected. It may just be the lighting, but they look shallower than I would’ve thought. Sometimes that happens when the impacted body is soft, like ice or loosely packed material — though we know the surface is rocky. Maybe it’s powdery, like the Moon’s surface? There are grooves, too, possibly cracks in the surface. Stress fractures from an impact?

It’s too early for me to speculate much, and I’m no expert, but this certainly whets my appetite to see what happens when Dawn slips into orbit and starts taking high-res images of the surface!

That will happen tomorrow, when I am at The Amaz!ng Meeting 9 in Las Vegas. I’ll be pretty busy with that (and trying to blog and tweet about it too) but I’ll do what I can to report on what I hear about Dawn and Vesta. In the meantime, keep your eyes on the Dawn mission homepage and The Planetary Society blog for info.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA


Related posts:

On approach to Vesta
Asteroid comparison chart, Part II
Hubble spins an asteroid

MORE ABOUT: asteroid, Dawn, Vesta

Comments (29)

  1. kevbo

    Note that you can click on the image to envestulate it.

  2. WJM

    flattened mildly-lumpy spheroid

    “Potato-shaped”, surely? Remember the Solar System Shape Rule: everything is either spherical or potato.

  3. Sparky

    As I understand it, Dawn won’t be doing any serious science until August, since the engineering side of things want to be sure Vesta is in a safe orbit before they do anything else.

  4. Is that the giant southern-hemisphere crater we’re looking at, with the central peak to 7 o’clock of center? If so, it’s… softer than I expected.

  5. Grand Lunar

    That looks like some interesting terrain there.
    I can hardly wait for some close ups!

    This mission is one example of what we, as a species, can do. We’re about to actually orbit a relic from the solar system’s past, for the first time!
    I wonder what mysteries await….

  6. Mount

    “…and I’m no expert” lol wut?

  7. Chris A.

    @Grand Lunar:
    “We’re about to actually orbit a relic from the solar system’s past, for the first time!”

    I think the folks on the NEAR-Shoemaker mission would dispute this statement.

  8. John Moore

    I guess the moon itself does not qualify as a relic from the solar system’s past?

  9. Dave R

    >530 km (260 miles)

    330 miles?

  10. Paul

    What’s with the extreme rationing of images? One nav image a week? It seems stupid. The probe could blink and die any minute (it’s not like space has been that kind to earthly technology), and this is all we’d ever have. Hell, we don’t even have a single complete rotation set. Weird.

  11. Anchor

    @#4 Matt, yes, I think it is that putative ‘central peak’ which has been tentatively interpreted (from Hubble Space Telescope images) to be the result of a huge impact that is thought to have knocked away nearly an entire hemisphere of Vesta. The lower-res image released previous to this one (acquired on July 1) shows the same feature, with Vesta rotated:

    http://www.nasa.gov/mission_pages/dawn/multimedia/dawn-image-070111.html

    It sure does appear to have suffered plenty of erosion, doesn’t it?

    Those parallel grooves strongly remind me of what we see on Phobos. One mechanism that has been put forward to explain Phobos’ system of grooves is that Phobos had episodically passed through swarms of impact ejecta debris tossed up by big impacts on the Martian surface as Phobos orbited Mars.

    If the grooves on Vesta were caused by a similar mechanism, we at once encounter a number of very intriguing questions.

    The main one is the source of a dense swarm of debris capable of scouring Vesta like that: Vesta (currently at least) doesn’t orbit another large body that could have sprayed it with impact ejecta debris, and the asteroid belt has for at least 3 billion years been far too sparse to supply anything near like the population density to create a coherent system of parallel grooves like that.

    If the debris-swarm explanation for the parallel grooves is correct, then the debris would have to have come from an impact on Vesta itself (perhaps this big impact) with some portion of the rubble gravitationally gathered in a relatively dense swarm or ‘cloud’ as it briefly orbited Vesta (the tidal gradient is slight but perhaps sufficient to keep such a swarm-cloud from consolidating into a single body) before it rained back onto Vesta and scoured the surface at relatively very low energy. It will be interesting to see how (or whether) the surface is similarly marked elsewhere…

  12. Grand Lunar

    @Chris A

    Dang it, how could I forget NEAR-Shoemaker?!
    :(
    Thanks for the correction.

    @John Moore

    Good point.

    Technically, maybe Earth counts too. It just has a younger surface. :)

    Ares there any first time achievements for Dawn, then?

  13. Paul

    Grand Lunar,
    “Ares there any first time achievements for Dawn, then?”

    First mission to enter orbit around a main-belt asteroid.

  14. Steve

    Given the three craters in the bottom left corner…..it looks like a lumpy bowling ball.

  15. Eddie Janssen

    I thought I saw the face of Jesus, but no.

  16. Egad

    Ooo! Grooves! And a crater chain!

    What’s with grooves — they’re all over the place it seems.

    I can’t wait to see the abandoned Krell science station.

  17. Paul from VA

    Sooo tantalizing but clearly they are sitting on the scientifically interesting data (which I find kinda irritating). The big question for Vesta is whether it has an enormous impact crater, which has been suggested by optical and radio data. This doesn’t look like that side of vesta though. Can’t wait for a full surface map.

  18. Kappy

    @Grand Lunar – There are a bunch of first time achievements for Dawn:

    First space probe to enter orbit without a close fly-by first.
    First orbiter to orbit an object in the solar system, break orbit, then enter orbit around a second body (assuming it gets away and then enters orbit around Ceres in 2015)
    First to visit and image Vesta & Ceres (the two largest asteroids)
    First to visit an asteroid that is a differentiated body (assuming Vesta is, otherwise Ceres almost certainly will be)
    It’s got ION engines, I’m not sure but it might be the first probe using Ion engines to actually do science (rather than just testing)
    It’s the first spacecraft that can change its speed by more than 10km/s AFTER separation from its launch vehicle.

    There are probably many others I can’t think of right now.

  19. Joel

    Oooh, can’t wait to see more.

    @16. Egad – Monsters from the Id. That’s what really blew half of the asteroid away.

  20. tmac57

    @Eddie 15- “I thought I saw the face of Jesus, but no.”
    I see Snoopy looking toward the left and slightly downward.

  21. tmac57

    I also see the head of a baby seal,right about 3 o’clock.Very striking,that one.Check it out.

  22. VinceRN

    I love this mission, it’ll do a lot of great science and give us fantastic pictures to look at, and proving that we can leave orbit of one body and go to a second, and possible even leave that, opens up a lot of future possibilities.

  23. @Paul from VA: I think it IS that side of Vesta. We’re looking at the giant crater, if that is what it is, almost straight on. The lump near the middle of the picture is the south polar central peak.

    As Anchor said, it looks eroded.

  24. Sam H

    @18 Kappy: The first probe with ion engines to perform valuable science was Deep Space 1 – it flew by both asteroid Braille and comet Borrelly, returning many high-res images of the later. It’s apparently still out there with engines offline but communications remaining active – in case it’s ever needed again.

  25. There was at least one other ion-powered space probe: the European Moon probe SMART-1. It took an awfully long time just to get to the Moon, but it did it using an ion engine for the cruise phase.

  26. Oh, geez, and how could I have forgotten Hayabusa? That used ion thrusters as well.

  27. Awesome! Can’t wait for more – and to see Ceres in such detail too. :-)

    Wonder if we’ll find any moonlets orbiting either of these worlds?

    @18. Kappy :

    @Grand Lunar – There are a bunch of first time achievements for Dawn:
    First space probe to enter orbit without a close fly-by first.
    First orbiter to orbit an object in the solar system, break orbit, then enter orbit around a second body (assuming it gets away and then enters orbit around Ceres in 2015)
    First to visit and image Vesta & Ceres (the two largest asteroids)
    First to visit an asteroid that is a differentiated body (assuming Vesta is, otherwise Ceres almost certainly will be)
    It’s got ION engines, I’m not sure but it might be the first probe using Ion engines to actually do science (rather than just testing)
    It’s the first spacecraft that can change its speed by more than 10km/s AFTER separation from its launch vehicle.
    There are probably many others I can’t think of right now.

    How about this one? :

    First to visit an ice dwarf type planet – Ceres being mostly water apparently with Dawn flying by that largest asteroid and smallest “four -and-a-halfth planet” planet* in February 2015 a near tie but just pipping New Horizons (flying past Pluto on the 14th July 2015) for that honour.

    Assuming all goes to schedule.

    Source : the respective Wikipedia pages for the Dawn and NewHorizons missions.

    * As Isaac Asimov put it :

    “… he had left out a planet. It was not his fault; everyone leaves it out. I leave it out myself when I list the nine planets, because it is the four-and-a-halfth planet. I’m referring to Ceres; a small but respectable world that doesn’t deserve the neglect it receives.”

    – Page 63, chapter 5 “The World Ceres” in ‘The Tragedy of the Moon’ by Isaac Asimov, Mercury Press, 1973.

    In that same essay – which I’d highly recommend – Asimov sugggests that for a number of reasons Ceres may one day (or decade or century) “be the astronomical centre of the solar system.” (Page 66, Asimov, 1973.) I hope Asimov’s right and I certainly agree with him that Ceres and the other small planets in our solar system deserve more respect and generally hold a great deal that’s of interest.

  28. Calli Arcale

    Kappy:

    It’s got ION engines, I’m not sure but it might be the first probe using Ion engines to actually do science (rather than just testing)

    Don’t say that to the Deep Space 1 team. While one of the major goals was engineering validation of deep space ion propulsion, they also did considerable science. Their primary science target was the asteroid 9969 Braille, and they also encountered Comet Borrelly twice. They actually did science out there, not just engineering. ;-)

  29. Success! Dawn has successfully entered orbit around Vesta! :-)

    Click on my name for more via a space-dot-com news item. :-)

    Congratulations and thanks to all the people of the Dawn mission. :-)

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

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

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »