MESSENGER at Mercury: HAWESOME

By Phil Plait | January 15, 2008 8:24 pm

Welcome DailyKos folks once again! I see Darksyde linked here, so thanks for visiting. I suspect you’ll like my stance on politics, too, so check out, for example, my post on Mullah Huckabee and the rest of the site. Enjoy!

Update II: Emily has a lengthy discussion of this image, with some typically fine insight.

Whoa. Just: whoa.

This is the highest res image yet returned from the MESSENGER spacecraft of Mercury, taken when it was 27,000 kilometers from the planet (after the encounter).

Mercury rotates three times on its axis (a "day") for every two times it goes around the Sun (a "year"), so there is all sorts of weird phasing that goes on (something like the Moon always showing the same face to Earth, but a bit more complicated). Not only that, but its orbit is highly elliptical, ranging from 46 to 70 million km from the Sun. All this together means that the same half of Mercury is facing the Sun every other* time it reaches perihelion (closest point in its orbit to the Sun).

Do you see that circular feature to the upper right, slightly lighter in color than the surrounding plains? That’s Caloris Basin, the Basin of Heat. It’s called that because when Mercury reaches perihelion, that spot is close to being aimed right at the Sun. It’s one of the worsts spot on Mercury to live, if you’re considering a winter home there. Caloris Basin (formed in some ancient and very large impact) is over 1300 kilometers across — roughly as big as Texas. The mountains ringing it are 2 km high.

Because of the weird spin/orbit coupling, when Mariner 10 passed Mercury in 1974, it never was able to see the western rim of Caloris Basin. But there it is, right there, seen by human eyes for the very first time.

Awesome.

The cratering is lovely. Mercury is literally saturated with craters; a new impact is likely to wipe out more craters than it would form. There are rays visible, too, streaks of material ejected after an impact. We see those on the Moon as well. It looks like there are more craters near the left edge, but I think that’s an illusion; to them the Sun is low on the horizon and rim shadows are longer. That exaggerates the crateriness of the craters there, while ones under the Sun have short shadows, making them hard to see.

All in all, wow. Wowee wow wow.

And this is just the first close up image! We’ll be getting more in a few days, and then more again in the next flyby, and then, in 2011, we’ll get as many images of this tiny, hot, battered, dense and neglected planet as we can handle.

Look what we did! Man, I love this stuff.

* Well, nuts. Commenter Solomon pointed out I messed up this description; I originally left the word "other" out. Oops. I put it in, and thank Solomon for finding this!

Comments (66)

  1. When I saw the picture (without reading anything else) I thought it was the moon. I guess I need to bone up on my astronomy.

  2. J. D.

    Those rays are actually canals! And the bright spots in the upper right hand part of the picture are produced by the bright lights of Mercurian cities! Why won’t you just admit what you KNOW to be true!? Enough of this NASA cover up!

    J. D.

  3. I put the blog post up in a hurry to get the news out, but now that I look at the image more, I am seeing more fascinating stuff.

    There are double-rimmed craters, and lots of scarps.

    The biggest ray system, in the middle of the image, comes from a perfect pinprick crater… that’s probably 30 km across. :-)

    There’s a crater at the bottom surrounded by an irregular apron of dark material.

    There are several very bright craters, like Aristarchus on the Moon.

    I don’t see a lot of big impact events (besides Caloris Basin). Zillions of little craters, fewer bigger ones, and then suddenly none much bigger. On the Moon, you see craters ranging in size up to about the size of Clavius, then you get maria and basins.

    There is, however, a thick dark ring smaller than Caloris to the lower right, at about 4 o’clock, just above the bright crater with the dark rim and rays. What’s that?

    I need to look over the Mercury maps from 1974.

    This is incredible. I’ll be very interested to read what Emily says.

  4. Stuart: No worries mate, if I hadn’t read the accompanying text, I would have said, “yeah, okay, it’s the moon – and?” :)

    Phil: Just an FYI, I’m getting this error at the top of the comment captcha screen:
    Warning: Cannot modify header information – headers already sent by (output started at /home/badastro/domains/badastronomy.com/public_html/bablog/wp-content/plugins/SK2/sk2_second_chance.php:2) in /home/badastro/domains/badastronomy.com/public_html/bablog/wp-content/plugins/bad-behavior/bad-behavior/screener.inc.php on line 8

  5. Ken_g6

    For reference, the Solar System Simulator shows what Mariner saw, as given on Emily’s blog:

    LINK

    And yet I’m still not sure which feature is Caloris basin. Is it the well-defined cut-off crater just above the equator, or the less-well-defined light area above that?

  6. Rob in PA

    “…seen by human eyes for the very first time.”…..chills running down my spine….think of the eons. It always amazes me how un-different the planets and moons of our solar system are. They are familiar. Mercury looks like our moon. Mars looks like the high desert (except for those blackberries!), even down to the dust devils. The giants and their weather. The giant’s moons with volcanoes, lakes, tektonics etc.. And yet the differences and complexities astound…a hallucination of our own back yards! We’ve so much to learn, what will Mercury teach us?

    thanks, BA

  7. Christian X Burnham

    OK, Redditted. (The squeaky astronomer gets the grease.)

  8. Huron

    I can’t wait for more images to be released, it is hard to believe that it will just get better from here.

    It is about time that we got back to Mercury.

  9. Nygard

    I’m really intrigued by the double crater at about 11 o’clock, near the terminator. It looks like two almost perfectly concentric crater rims.

    Is there a single-impact configuration that could do that? Or would that necessarily result from two impacts that randomly aligned?

  10. I need to look into this more, but I’m sure it’s an impact event. The crater’s rims are HUGE. There are double-rimmed craters on the Moon like that, but they are usually small, far smaller. I have always wanted to learn more about impact geology on other planets, so this is my chance.

  11. Solomon

    I hate to be a spoilsport; but, something in this post doesn’t make much sense. You say:

    “Mercury rotates three times on its axis (a “day”) for every two times it goes around the Sun”

    And then claim that this implies:

    “the same half of Mercury is facing the Sun every time it reaches perihelion”

    This just doesn’t work. If Mercury rotates three times for every two orbits, then after a single full orbit, it will have rotated 1.5 times, meaning that it is facing the exact opposite direction as at the previous perihelion. So, it seems that Caloris Basin could only be directly facing the sun at every other perihelion.

  12. D’oh! Left a word out. Fixed. Thanks.

  13. csrster

    I’ve heard David Grinspoon illustrate the rotation/orbit resonance of Mercury at a bookreading by drumming out a polyrhythm. No wait, I lie, it was actually the resonance between the orbits of the Earth and Venus.

  14. Chip

    BA thanks for pointing out some features! Wild – Mercury is lunar-like but not lunar-like. I’d love to be a fly on the wall where geologists are discussing this. ;)

  15. Huron

    Anyone else see the classic alien face in the picture? About 2/3 of the way up, near the terminator.

  16. BigBob

    Woooooooooooooo
    Take me there. Now!

    Big thanks to all the guys and gals involved in this investigation. Our dreams are coming true.
    I going to print off a huge picture and plot everyone’s observations (and make plenty of my own).

    Bob(Biiiiiiiig)

  17. BigBob

    > The Bad Astronomer on 15 Jan 2008 at 8:40 pm
    > The biggest ray system, in the middle of the
    > image, comes from a perfect pinprick crater
    > that’s probably 30 km across.

    See about 500k to the left is an old impact crater with a new one dead centre. Very prominent even for Mercury.

    # Nygardon 15 Jan 2008 at 9:44 pm
    > I’m really intrigued by the double crater at
    > about 11 o’clock, near the terminator. It looks
    > like two almost perfectly concentric crater rims.

    # The Bad Astronomeron 15 Jan 2008 at 10:00 pm
    >I need to look into this more, but I’m sure
    > it’s an impact event. The crater’s rims are HUGE.

    If I ramp up the zoom to 300% I see a massive fold in the crust that reaches right through the outer rim of that double crater at 12 o’clock. The whole area around that double crater is peppered with tiny craters while the area about 200k to its right is relatively (relatively) smooth.

    Can’t get enough of this.

    BTW to increase your viewing pleasure, read the big image into a good image application that allows you to enhance the contrast. That will reveal even more features that are otherwise obscured beyond the terminator.

    Bob

  18. Grand Lunar

    Mercury bears superficial resemblence to Ganymede, don’t it?
    I mean, look at those bright spots. Ganymede has something that looks like those.

    Don’t think I’d confuse the Moon for Mercury. No seas!

    What other secrets might the iron planet have for us?

  19. Nigel Depledge

    Grand Lunar, I thought more of Callisto than Ganymede, but I do see what you mean.

    Thanks again, BA. Another good ‘un.

  20. bønez_brigade

    I was also curious of the huge crater(s) at ~11 o’clock. Before I read the captions, I thought _that_ was Caloris Basin — only to be cut off… again!

  21. Michelle

    If we never seen Caloris Basin before, how did we know it was there…?

  22. Grand Lunar — the bright spots are probably just a photographic effect, and might go away at a different angle. Then again, they might not. Something to check out, surely.

  23. Rav Winston

    Fweakin’ cool!

  24. BA — are there any readings yet from instruments other than the cameras? I mean, can we determine (or redetermine) Mercury’s albedo, mass, coefficient of moment of inertia, magnetic field strength…? Observation is lovely, but half-assed amateur astrophysicists like me live for the numbers. My big problem with Cassini was that I had to wait years just to find out what the pressure and temperature readings were at Titan’s surface, something we got from Viking on Mars right away. What’s up with that? Just ESA versus NASA?

  25. Moose

    You know, at the half-way point of this Canadian Winter, the Caloris Basin is looking awfully tempting…

  26. Larry

    Wait a minute! That’s no moon, that’s a spa…[slap!]

    Oh, excuse me, my inner geek took control for a second. Seriously cool picture, though. What a violent place the early solar system must of been. Like our moon, you seen craters within craters within craters.

    Is there a really large version of this image available? The linked picture is a bit larger but I’d like to really zoom down.

  27. Ginger Yellow

    “Do you see that circular feature to the upper right, slightly lighter in color than the surrounding plains? That’s Caloris Basin, the Basin of Heat. ”

    No it’s not. It’s the planet destroying laser.

  28. Darth Robo

    Very cool! The Messenger site says it should get some colour photo’s soon, so I can’t wait for those. One question though, what are the bright white bits exactly? According to wiki, it implies Mercury isn’t volcanically active anymore, so are the white bits just tiny craters from fast but small meteorite impacts?

  29. Darth Robo

    “It’s the planet destroying laser.”

    The Rebels have got ahold of the plans! Dammit! >:-(

  30. kingthorin

    “Mercury rotates three times on its axis (a “day”) for every two times it goes around the Sun (a “year”)”

    3 days over two years, does that mean that every other year is a leap year? Or is a year simply 1.5 days? Hmmmm the Mercurian calendar seems confusing.

  31. Mark Martin

    Darth Robo,

    That’s essentially right; the white spots are fresh ejecta from impacts. The brighter ones appear to be rather localized. But there’s one interesting one over just a bit to the upper-left of dead-center. It’s a comparatively small, sharp crater with an ejecta blanket that’s spread out for hundreds of miles with lots of filamentary structure to it.

  32. Mark Martin

    I wonder if Mercury will eventually be on Clickworkers? It certainly is ripe for it.

  33. aiabx

    I’ve seen Mercury through a telescope, and it is nothing like this. This is freakin’ awesome. Who wants to take bets on active volcanoes, with those big solar tidal effects?

  34. For those who, like me, are inspired to learn more about Mercury, here’s a link to Wikipedia:

    http://en.wikipedia.org/wiki/Planet_Mercury

  35. Tom

    Wow! Just a couple weeks into the new year and we got our first images back from another world. Great way to start the new year!
    Woooo! :D

  36. Ryan

    The _really_ cool thing about MESSENGER is the magnetometer measurements it will bring back. Mariner 10 had 2 observations lasting for less than an hour each, so all we were able to determine was that it had a magnetic field, and that it was roughly dipole (iirc 300 nT-Rm where Rm is the radius of Mercury). The Mariner 10 data is too poor (both spatially and temporally) to get any higher multipole moments.

    It turns out that this is really huge to be explained by crustal rocks, which means a planetary dynamo is likely (although it would have to be a rather weak dynamo, iirc the field is 1/100th that of Earths).

    The problem is that given a planet Mercury’s size, made of iron, it would be solid by now, whereas a planetary dynamo requires a liquid core, so what gives? Well as it turns out if you put ~1-3% sulphur (that number might be off by one or two percent, I am quoting from memory) in the core you raise the freezing point of iron to the point where you can get a thin outer liquid shell where a dynamo can happen.

    Exciting stuff, I can’t wait to see what comes from it

    **Disclaimer, I am a grad student who will be doing research on planetary dynamo theory (once I finish my courses), so I might be slightly biased when it comes to the most interesting data from Messenger. Also, all this stuff is quoted from memory so there is a good chance it is dead wrong**

  37. Hoonser

    Nice try. That’s clearly the moon!

  38. BigBob

    > kingthorinon 16 Jan 2008 at 7:47 am

    > “Mercury rotates three times on its axis (a “day”) for every
    > two times it goes around the Sun (a “year”)”

    > 3 days over two years, does that mean that every other
    > year is a leap year? Or is a year simply 1.5 days? Hmmmm
    > the Mercurian calendar seems confusing.

    It gets worse kingthorinon.

    Mercury’s rotation i.e. one turn on its own axis as measured against the stars, takes 58.65 Earth days. That’s exactly two thirds of the time the little planet takes to get once around the Sun (87.97 Earth days). So 3 rotations per 2 orbits makes Mercury’s spin/orbit ratio 3:2. It seems to be because of Mercury’s orbital eccentricity. It does strange things to the tides. Someone less compost mentis than I has done the maths. It turns out that if Mercury were in a perfectly circular orbit at its perihelion (0.31 AU) it would be tidally locked on a 1:1 spin / orbit ratio just like the Moon is with respect to the Earth. Tides eh?!

    However, we measure days in terms of midday to midday right? So a Mercurian day (midday to midday) takes 2 x 88 = 176 Earth days.

    Aspirin?
    BigBob

  39. Hoonser — I know you’re joking, but just in case some pseudoscientist tries taking this seriously, look at the photo again — no maria. And it doesn’t look like the Lunar far side because that looks much thicker with craters.

  40. Ian

    “Mercury is literally saturated with craters; a new impact is likely to wipe out more craters than it would form.”

    I’m picking at nits here, but from a planetary formation standpoint, how is this possible? When the planet was young, there were few craters, so the number of craters destroyed by the average impact would have been close to zero. As the number of craters increased, the number of craters destroyed on average would also increase until it approached the number of craters created on average; at which point the crater system would be in equilibrium, and the total number of craters would be approximately constant. But your statement implies that the crater system has actually gone past equilibrium, which makes no sense.

  41. Libraryguy

    Quick Question: could Mercury be the remains of a gas giant?

  42. andy

    Libraryguy: according to this paper (unfortunately tucked away behind the Nature firewall), a Jupiter-like planet’s atmosphere starts evaporating when it gets closer than about 0.16-0.14 AU from a solar type star. So gas giants should survive fine at Mercury orbit (0.38 AU), which means it is unlikely that Mercury is a gas giant core.

    (Plus, if core accretion is correct, the minimum size of a gas giant’s core should be somewhere around 6-10 Earth masses, which is a LOT bigger than Mercury)

  43. Matt J

    Ok, this is because I am either blind or just unobservant, but could somebody draw some lines on the hi-res pic pointing to where this Caloris Basin is supposed to be? I just see a whole bunch of small craters, and my complete lack of astronomical experience doesn’t exactly help things.

  44. Michael Amato

    It seems to me Mercury has more bright crater rays than the moon does. I wonder what this means. I have often looked at mercury with telescopes and sent sketches to The ALPO Mercury section. In a good telescope anyone can see The Coloris Basin.

  45. Libraryguy

    Thanks for the info, andy.

  46. Phy

    Matt, check out Emily Lakdawalla’s page that Phil links to in the update at the start of his post. She highlights where she thinks most of it is.

    On the gas-giant-core-thing, would a naked core not look substantially different than the not-quite-Luna that Mercury presents? Setting aside the issues of the distance at which the atmosphere would be stripped, and the probable mass of the core, I mean. I assume much of the cratering we see on other airless bodies in the solar system was inflicted shortly after the planets coalesced, when potential impactors were more numerous. If Mercury was a giant, wouldn’t its core have escaped much of the cratering, due to potential impactors exploding in the atmosphere, or have seen it erased due to atmospheric erosion?

  47. rusto

    Non-astronomer astronomy question: it appears that all of the craters were created by impacts from objects that were traveling towards Mercury’s center (or perpendicular to it’s surface)… I would think you’d have many more craters that were oblong due to (in my mind) more common non-perpendicular trajectories.

  48. American Voyager

    January 14th must be a special day for “new” worlds. MESSENGER makes its first closest approach to Mercury revealing never before seen parts and three years ago on 1/14/05 we land on Titan. I’m going to have to mark this date as “the” space anniversary. Any more important events happen on this day that I’m not aware of?

  49. Jeffersonian

    It’s an educational experience coming here to BA. Knowing (relatively) little about astronomy I don’t have the level of understanding you have, Phil, but yet I can’t get over the fact that I’m sitting here looking at this picture (and while simply sitting in front of a monitor; s’like living in the future).

  50. Nigel Depledge

    Very good background on Mercury here, guys:
    http://www.nineplanets.org/mercury.html

    (Hmmm, maybe Bill needs to register “eightplanets.org” to keep up with the IAU…?)

  51. MaDeR

    Probably not. Too far away from Sun to be a core remnant of hot jupiter.

  52. Darth Robo

    Mark Martin, muchas gracias! :)

    That tiny crater you pointed out, I would hazard a guess that it would have been made by something fairly brittle and of low mass? As opposed to a heavier object whose ejecta wouldn’t travel as far and may appear more uniform. Total guess though, I’m no astronomer, just a total amateur. It is an interesting one, I wouldn’t have spotted it otherwise.

  53. American Voyager says: “January 14th must be a special day for “new” worlds. MESSENGER makes its first closest approach to Mercury revealing never before seen parts and three years ago on 1/14/05 we land on Titan. I’m going to have to mark this date as “the” space anniversary. Any more important events happen on this day that I’m not aware of?”

    I don’t know of any specifically on the 14th, but we are coming up on “hell week” for NASA. All of the loss-of-life mission accidents in its history have occurred within the seven day stretch at the end of January:

    Apollo 1 fire – 27 January 1967
    Challenger – 28 January 1986
    Columbia – 1 February 2003

    This does not include deaths in training accidents, etc.

    - Jack

  54. kingthorin

    Thanks BB, yes I’ll take the Asprin :D

  55. nonner

    Mercury looks like more proof that thermal events happned that created enough heat to boil the planet and cause the incredible number of collapsed bubbles we see now . This of course explains the perfect circular craters with the plops or drops in their centers.

  56. nonner

    Double cratering is , mentioned by Nygard , is the result of a great bubble collapse and the wave created inside the crater after said collapse of magma and semi-solid layers of this doomed planet.

  57. Update : Tonight MESSENGER is again flying by Mercury dfor thesecond time inits October 2008 fly-past.

    This thread is linked to that and now if youclick my name the link should take you back to the latest Bad Astronomy ‘MESSENGER-flies-by-Mercury’ thread.

    Providing it works … lets see ..

    PS. Oh & more good news – Huckabee didn’t make McCain’s Vice-Presidential choice or Republican nomineee and looks like fading away with his 15 minutes of fame (too long IMHO) well and truly over … The bad news o’course being that Sara Palin seems like a female Huckabee clone.

  58. I wondered :

    “Update : Tonight MESSENGER is again flying by Mercury for the second time in its October 2008 fly-past. This thread is linked to that and now if youclick my name the link should take you back to the latest Bad Astronomy ‘MESSENGER-flies-by-Mercury’ thread. Providing it works … lets see ..”

    Well I’ve just checked &, yes, the links working so you can click there to come here and click my name here to go back there folks. :-)

    Hope that is okay netiqutte-wise. Am trying to make things easier for fellow posters here. Please let me know if this is considered bad form or anything like that – don’t think it is, obviously, but not really too sure ..

    Actually thinking netiquette is there a problem with acronymic names like MESEENGER which, being in all-capps, is like SHOUTING in net-ese? :-( Would it be more polite or less (certainly less accurate I ‘spose) to have MESSENGER written in lower-case ie. Messenger instead? Oh, & then if it is lower case there’s always the risk of confusing the spaceprobes name with the word ‘messenger’ itself .. Hmmm …

    Tongue-twister potential here :

    The MESSENGER team’s messenger came with the message that mercury had been discovered on Mercury and also that because saying MESSENGER not messenger sounds like shouting on-line the MESSENGER teams’ messenger wanted us to use ‘messenger’ instead of ‘MESSENGER’ – except for when also mentioning the MESSENGER’s teams messenger! ;-)

  59. joe nahhas

    Kepler (demolish) Vs Einstein’s

    Areal velocity is constant: r² θ’ =h Kepler’s Law
    h = 2π a b/T; b=a√ (1-ε²); a = mean distance value; ε = eccentricity
    r² θ’= h = S² w’
    Replace r with S = r exp (ỉ wt); h = [r² Exp (2iwt)] w’
    w’ = (h/r²) exp [-2(i wt)]
    w’= (h/r²) [cosine 2(wt) - ỉ sine 2(wt)] = (h/r²) [1- 2sine² (wt) - ỉ sin 2(wt)]
    w’ = w’(x) + ỉ w’(y) ; w’(x) = (h/r²) [ 1- 2sine² (wt)]
    w’(x) – (h/r²) = – 2(h/r²)sine²(wt) = – 2(h/r²)(v/c)² v/c=sine wt
    (h/ r²)(Perihelion/Periastron)= [2πa.a√ (1-ε²)]/Ta² (1-ε) ²= [2π√ (1-ε²)]/T (1-ε) ²

    Δ w’ = (d w/d t – h/r²] = -4π {[√ (1-ε²)]/T (1-ε) ²} (v/c) ² radian per second
    Δ w’ = (- 4π /T) {[√ (1-ε²)]/ (1-ε) ²} (v/c) ² radians
    Δ w’ = (-720/T) {[√ (1-ε²)]/ (1-ε) ²} (v/c) ² degrees; Multiplication by 180/π
    Δ w’ = (-720×36526/T) {[√ (1-ε²)]/(1-ε)²} (v/c)² degrees/100 years
    Δ w” = (-720×3600/T) {[√ (1-ε²)]/ (1-ε) ²} (v/c) ² seconds of arc by 3600

    Δ w” = (-720x36526x3600/T) {[√ (1-ε²]/(1-ε)²} (v/c)² seconds of arc per century
    This Kepler’s Equation solves all the problems Einstein and all physicists could not solve

    The circumference of an ellipse: 2πa (1 – ε²/4 + 3/16(ε²)²- –.) ≈ 2πa (1-ε²/4); R =a (1-ε²/4) v=√ [G m M / (m + M) a (1-ε²/4)] ≈ √ [GM/a (1-ε²/4)]; m<<M; Solar system
    Advance of Perihelion of mercury.

    G=6.673×10^-11; M=2×10^30kg; m=.32×10^24kg
    ε = 0.206; T=88days; c = 299792.458 km/sec; a = 58.2km/sec
    Calculations yields:
    v =48.14km/sec; [√ (1- ε²)] (1-ε) ² = 1.552
    Δ w”= (-720x36526x3600/88) x (1.552) (48.14/299792)²=43.0”/century

    Conclusions: The 43" seconds of arc of advance of perihelion of Planet Mercury (General relativity) is given by Kepler's equation better than all of Published papers of Einstein. Kepler's Equation can solve Einstein's nemesis DI Her Binary stars motion and all the other dozens of stars motions posted for past 40 years on NASA website SAO/NASA as unsolved by any physics

    Anyone dare to prove me wrong?

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