MESSENGER's family portrait

By Phil Plait | February 18, 2011 10:30 am

On March 17, just a month from now, NASA’s MESSENGER probe is scheduled to enter orbit around Mercury, the smallest planet in the solar system. No other mission from Earth has ever done this, and for the first time we’ll get high-resolution maps of the entire globe.

On its way down, the spacecraft was commanded to turn around and look outward, toward space. It took a series of images of what it saw… this astonishing family portrait of the solar system:

Click it to ensolarsystemate it and see it in more detail. When you do you’ll see the five classical planets in our system, as well as the Earth and Moon. Uranus and Neptune are there, but too faint to see, unfortunately, but still, this is an interesting picture. In November 2010, when these pictures were taken, Mercury was still nothing more than a dot. In fact, all the planets as barely more than dots, a reminder that this probe is well away from home and nowhere near any solid ground.

I like very much the images of Venus and the Earth. Venus is technically the closest planet to MESSENGER besides Mercury, though it depends on where the planets are in their orbits. It’s extremely bright as seen from the spacecraft, since MESSENGER is inside the orbit of Venus: the planet is therefore close to being full (like the full Moon) and reflects a lot of light back to the cameras.

And the Earth is accompanied by the Moon! That always amazed me. I’m so used to seeing pictures of just the Earth from space that it’s easy to forget that the Moon travels along with us. An important reminder in this picture is just how far the Moon is from us; 400,000 km is over 100 times the Moon’s size, so it appears to be a dot located well away from its home planet. If you wanted to make a scale model of it, a good way would be to use a golf ball to be Earth, and a marble located a meter away to be the Moon. That really brings home — ironically! — how small and distant our Moon is.

If you look to Jupiter you can see it has a couple of moons near it as well. The four moons spotted by Galileo 400 years ago are pretty big; Ganymede is actually about the same size as Mercury itself! Were Jupiter not there, Ganymede might be considered a planet on its own.

I smiled when I saw the section of the picture between Jupiter and Mars — that fuzzy glow is the Milky Way itself! The split down the middle is a dead giveaway; that’s caused by dust located in the disk of our galaxy. That section of the sky looks toward the center of our galaxy in the direction of the constellations Scorpius and Sagittarius.

I mention that last part on purpose. These probes we send out commonly only return pictures of the planets at which they’re aimed. Cassini sends us close-ups of Saturn, the fleet of craft orbiting Mars show us the Red Planet, and so on. It’s easy to get swept up in those fantastically detailed maps of alien worlds that they send back. But don’t forget the grand picture; when you go outside and look at the sky, that’s essentially the same view those spacecraft have! The Milky Way you see streaming across the night sky (if you’re in a dark location) is the very same sight seen by MESSENGER as it approaches Mercury, millions of kilometers away. Seeing the bulge of our galaxy toward Sagittarius from my back yard and seeing it in a picture returned from a spacecraft is, to me, a thrilling reminder that while we may be stuck here with our feet on the ground, our ideas have been launched into space to explore every corner of the solar system we can.

We’re pretty cool sometimes, we humans.

And as I’m sure many of you thought when you saw that picture, it’s much like the solar system family portrait taken by Voyager 1, seen from the outside in. So what better way to leave this post than with some of the finest words ever written by a human, inspired by that photo: the section of Cosmos called Pale Blue Dot, penned by humanity’s scientific poet laureate, Carl Sagan.


Related posts:

- Watermelon planet
- MESSENGER at Mercury: HAWESOME
- Spiders on Mercury
- Mercury hides a monster impact
- MESSENGER: three days out from Mercury
- MESSENGER’s third tryst with Mercury

Comments (51)

  1. Coyote

    Truly fantastic. I especially like how Saturn appears to be slightly oblong rather than spherical – even at that distance you can tell the rings are there.

    Also, we miss you, Carl. <3

  2. Sisko

    From that distance you can tell that even the Earth and Venus have their rings :)

  3. Nicole

    Although I read your blog occasionally, astronomy is not really “my thing” and I mostly come here for further understanding of whatever end-times scenario is splashed on the news. To be frank, hugely macroscopic concepts scare the #&*@ out of me and every time I watch the Powers of Ten video I whimper and tremble.

    That said, I don’t know why, but I was weirdly moved by this picture. Still frankly terrified, but in a good way this time. It’s… exciting, somehow; I love as Coyote pointed out that you can see Saturn’s rings. I am thrilled by the shot of the Earth and the Moon together. Thank you for sharing this :) I may not always “get it” but I think I did this time.

  4. Josh K

    Great picture! As far as an image go, it really doesn’t seem like much at first, but when you stop and think about it, it’s truely awe inspiring. I LOVE how astronomy photos can do that.

    Phil, do you know if MESSENGER’S orientation was completely perpendicular to the Earth and the Moon. Is that an accurate representation of how far the Moon is away from Earth?

  5. Rift

    “On March 17, just a month from now, NASA’s MESSENGER probe is scheduled to enter orbit around Mercury, the smallest planet in the solar system.”

    I thought at first, nu-uh, pluto is the smallest, and then it suddenly accured to me I’m never gonna get use to the fact that pluto ain’t a planet any more.

  6. Now that I think back, I can’t recall any images that have had both the Earth and the moon visible. Often it’s either the Earth from a vantage point too close to see the moon, or too far or with the moon not visible.

    Something that I never seem to realize with all the images of THINGS in space, is just how much emptiness is there. Occupied by a few rogue hydrogen atoms and some solar wind. I guess I have to feel a little bit of sorrow for MESSENGER’s quiet lonely trip. At least it’ll meet up with mercury soon…

  7. Matt B.

    But when we do colonize other worlds we might get something like on Futurama:

    Leela: Bender you’re harming the planet.
    Bender: Who cares? It’s not like it’s the only one we’ve got.

  8. “An important reminder in this picture is just how far the Moon is from us; 400,000 km is over 100 times the Moon’s size, so it appears to be a dot located well away from its home planet. If you wanted to make a scale model of it, a good way would be to use a golf ball to be Earth, and a marble located a meter away to be the Moon. That really brings home — ironically! — how small and distant our Moon is.”

    A moon globe which would be in scale with a 12 inch Earth globe would be a3.25″ in diameter. (see http://idea.uwosh.edu/nick/moon-earth_scale.pdf )

    Virtually every classroom in the world has a 12 inch earth globe. The separation at this scale would be 30 feet, about the dimensions of the average classroom allowing a really accurate display of an accurate model of the system.

    I think this would be a really cool demonstration of the scale of the earth moon system. I’d buy at least a couple.

    I’ve sent a product idea to Edmund Scientifics and Sky and Telescope, but I don’t have much hope they’ll go for it.

  9. DrFlimmer

    We’re pretty cool sometimes, we humans.

    Yeah, probably a little bit too “sometimes”. *sigh*

    (At first I thought, this comment would be kind of a party crasher. But with the Sagan quote, it fits perfectly, again.)

  10. Endyo:

    Now that I think back, I can’t recall any images that have had both the Earth and the moon visible.

    Well, they’re few and far between, but they’re out there. (Unless you count Apollo images, from which there are plenty to choose.)

    http://dotearth.blogs.nytimes.com/2008/03/04/on-the-dot-more-on-population-and-climate-questions/

    And what about the Earth, Moon, and Jupiter, as seen from Mars?

    http://www.msss.com/mars_images/moc/2003/05/22/index.html

    (Click the image on that page to embiggen. Perhaps Phil has a better term?)

  11. And what’s with all the gaps in the image mosaic? What’s NASA trying to hide? Did they accidentally see Nibiru?

    Oh, just in case —> :-) <—

  12. when you go outside and look at the sky, that’s essentially the same view those spacecraft have!

    Sometimes this applies to the planets, too. I think it was around 2000 that all the naked eye planets and the Moon were visible in the evening at once for a short while.

    I think artists’ impressions of exoplanetary systems foster (and may be influenced by) the idea that if one was somehow ‘up there’ with the planets they’d all appear as large globes. No, every clear night we’re on the observation deck of our own spaceship, if we want to be.

  13. Ed D

    A friend gave me an astronomy book from the 1890s and the author talked about looking up at the night sky from Venus and being able to see the Earth and Moon as naked eye objects. I have always loved that image; it’s nice to see an example of it in reality.

  14. 7. Rift Says: “…I’m never gonna get use to the fact that pluto ain’t a planet any more.”

    Such grammar! Everyone knows that it should be “pluto ain’t a planet no more.”

    - Jack

  15. Rift

    Sorry Jack,

    Bein’ here abouts all you edumacated city folks has ruined the rural jawin’ of this ole redneck…

    (If I may add, I went to the same University, University of Kansas, as Clyde Tombaugh did waaay back and I also studied astronomy. The big refractor there is named after him. And I am good friends with one of his grandsons. One of the malls in Kansas City has a fake telescope outside with Clyde’s name on it, that you can look through and see ‘Pluto’. Damn thing should be grandfather claused in as a planet. )

  16. Pluto will always be a planet to me. I’ll Photoshop a dot into this picture later.

  17. Jeff

    “No other mission from Earth has ever done this” – you have, maybe, evidence of a mission from elsewhere that has? :)

  18. Adrian Lopez

    It isn’t often that a picture makes the hairs on my arms stand on end, but seeing the label “Earth” next to that tiny little dot sure managed to do just that. Wow!

  19. Carolyn Ernst

    The caption posted with this picture on the MESSENGER website includes a link to a graphic showing the orientation of the planets (and Pluto) at the time the portrait was taken:
    http://messenger.jhuapl.edu/images/10-02131%20orbits-all.png

    Full caption:
    http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=399

  20. @#18 Mark:

    Preach it, brother!

    Uh, in a non-denominational way. And without a deity. =|

  21. Draa

    “We’re pretty cool sometimes, we humans.”

    Sadly, I think the uncool parts are beginning to outweigh the cool. Thanks Phil.

  22. Nick

    I’m sure it’s great how we’re going to be able to study the antipodal convergence in very high detail, but I’m still thinking… why are we studying Mercury? Why did a project like this get advanced funding over a Europa mission? I know we’re going to Europa, and I know it’s a more complicated mission, but we should already be flying around Europa by now. The mysteries of Europa are so much more tantalizing to me than impacts so large that they restructure planets… sorry Phil.

    Linaments > Jumble

  23. Messier Tidy Upper

    Superluminous. :-)

    Love this – great to have this grand planetary portrait taken this time from the opposite end of the solar system from the similar wonderful excercise as that captured from one of the Voyager spaceprobes. :-)

    @18. Mark & 21. gameshowhost :

    Pluto will always be a planet to me.

    Amen to that! Me too. :-)

    (I count all the ice dwarfs as planets just a smaller variety of planet just as gas giants are larger varieties of planets from ours. Planets big & small, yet planets all!)

    Preach it, brother! Uh, in a non-denominational way. And without a deity.

    Well, actually Pluto *is* a diety of sorts – the Roman god of the underworld. ;-)

  24. All these years I never realized the plane of the ecliptic was so catywampus to the galactic plane.

    Damn! We’re winging about all over the place!

  25. HP

    I love pictures of the Earth and Moon together (Messenger’s earlier pic is my desktop).

    As long as we’re reclassifying celestial bodies, can we just call the Earth-Moon system a binary planet? You know, Sol C1and Sol C2?

    Earth-moon really is quite a bit different than the situation with the other solar planets.

  26. JeremyC

    “No, every clear night we’re on the observation deck of our own spaceship, if we want to be.” – Vagueofgodalming

    An exquisite quote. Thanks!

  27. dustycrickets

    OT…sorry Phil…..but have you seen this…

    “Measles Outbreak Triggered by Unvaccinated Child”

    http://news.health.com/2010/03/22/measles-outbreak-triggered-unvaccinated-child/?pkw=outbrain-ha

  28. Bob

    @#10 Nick Dvoracek
    “A moon globe which would be in scale with a 12 inch Earth globe would be a3.25″ in diameter.

    Virtually every classroom in the world has a 12 inch earth globe. The separation at this scale would be 30 feet, about the dimensions of the average classroom allowing a really accurate display of an accurate model of the system.

    I think this would be a really cool demonstration of the scale of the earth moon system. I’d buy at least a couple.”

    What an incredible idea! The globes could easily be strung from the ceiling. This idea has great merit-every schoolroom should have an Earth-Moon System in scale. Then kids could really see the scale of the galaxy, which should help them grasp the scale of the cosmos (or at least our solar system and galaxy).

  29. molybdenumfist

    I have some pictures on my office wall of the Earth and Moon to scale and 3m apart. The sun would be a bit over a kilometer down the road at that scale. It makes you appreciate how small this rock is and how much black there is in between.

    In Melbourne here we also have a 1:1 billion scale model of the solar system that you can walk or ride a bike along too:
    http://www.portphillip.vic.gov.au/default/CommunityGovernanceDocuments/Solar_System_-_Self_Guided_Walk.pdf

  30. Messier Tidy Upper

    Pluto~wise the debate from the last “Planet X found?” thread continues here :

    http://blogs.discovermagazine.com/badastronomy/2011/02/14/no-theres-no-proof-of-a-giant-planet-in-the-outer-solar-system/#comment-359839

    with my (somewhat belated sorry) answers – comment #135 onwards – to CB & andy if anyone’s interested.

  31. Pete Jackson

    @27HP: Earth-moon were the only double planet until Charon was discovered in 1978, making Pluto-Charon a closer (both in size and distance) double planet than Earth-moon. But Pluto got demoted later to a dwarf planet, so we now have to consider dwarf planets in order to find other double planets.

    Q: If a dwarf star is still a star, why is a dwarf planet not a planet?

  32. DrFlimmer

    @ Pete Jackson

    Q: If a dwarf star is still a star, why is a dwarf planet not a planet?

    Especially, since every star is a dwarf star in its lifetime. Basically every star on the main sequence is a dwarf star (if I remember correctly).

  33. flip

    #10, 30, and #31

    I’m currently making scale planet puppets for a project – the first time I’ve ever made or even seen scale models – and not only is it fun, but it certainly does drum home how big/small everything is. My intention was to make finger puppets, but you quickly realise that Mars is way too small for that, and that Jupiter and Saturn are way too big. It’s an interesting exercise as a puppet maker, because of the scale, so instead of just finger puppets, I have all different types of puppets but in ‘planet’ form and to scale.

    Fun and educational!

  34. That bit from Sagan never fails to bring a tear to my eye. He had SUCH a way with words.

  35. Brian

    Just to be pedantic … the reading of Pale Blue Dot is not from Cosmos– whoever made this video used the Vangelis piece that is best known as the Cosmos theme, but Sagan wrote (and recited) these words years after Cosmos aired. Pale Blue Dot (the book) really would have made a great second series, I think.

  36. JB of Brisbane

    “Pale Grey Dot” – somebody had to say it.
    Also from the man himself, by way of Symphony of Science -
    “How lucky we are to live in this time – the first moments in human history when we are, in fact, visiting other worlds.”

  37. Tobin Dax

    All four Galilean moons are visible around Jupiter. How easily they can be seen always amazes me.

  38. réalta fuar

    To quote Mke Brown (before he went all political correct): “why should Pluto be considered a planet? Because 6 billion people think so.” Funny how he changed his tune once a few people decided he wasn’t the discoverer of the tenth planet after all.

  39. Messier Tidy Upper

    @ ^ réalta fuar : Good point – I think a lot of astronomers would have strongly disagreed with the anti-Pluto IAU definition before it was made and a lot still do.

    I think a majority of the public also disagree to the point where I expect (& yes hope) the IAU edict gets ignored and disdained in much the same way as many Catholics ignore some of the Pope’s silly decrees on contraception, etc ..

    If everyone ignores the IAU definition and no one uses it then I think that would be a great thing. Hopefully, it will lead to them recognising that they’ve made a huge blunder and then fixing it. Let’s have mass civil disobedience against the IAU planet-killers I say! 8)

    @34. DrFlimmer :

    @ Pete Jackson
    Q: If a dwarf star is still a star, why is a dwarf planet not a planet?
    Especially, since every star is a dwarf star in its lifetime. Basically every star on the main sequence is a dwarf star (if I remember correctly).

    Your memory is indeed correct – and I couldn’t agree more! :-)

    @36. Gary & 38. JB of Brisbane : Yes indeed. :-)

  40. Jabjabs

    It’s images like this that make you realize just how empty space really is. Very impressive indeed.

  41. JMW

    “And the Earth is accompanied by the Moon! That always amazed me.”

    Isaac Asimov wrote a Black Widowers story called “The Missing Item” which…hmm…well, it’s a factor.

  42. IanS

    @41 MTU,
    You seem to have a real bee in your bonnet about pluto, you don’t ever seem to argue for the promotion for the eleven other currently recognised dwarf planets in the kuiper belt or the two in the asteroid belt, why not? what is so special about Pluto?

  43. #27 HP, #33 Pete Jackson:
    Earth and the Moon are not a double planet, in the sense that Pluto and Charon are.
    Pluto and Charon are regarded as a double planet ( or double dwarf planet now! ), instead of a planet and satellite, for a very good reason; they are the only pair of planetary bodies in the Solar System, for which the barycentre lies in empty space between them.
    For all other planet-satellite pairs, the barycentre lies inside the primary body – including the Earth and Moon. Earth has 81 times the mass of the Moon, and their separation is only 60 Earth radii, so the barycentre lies inside the Earth – significantly displaced from its centre, but still inside it.

  44. Nigel Depledge

    Ed D (15) said:

    A friend gave me an astronomy book from the 1890s and the author talked about looking up at the night sky from Venus and being able to see the Earth and Moon as naked eye objects. I have always loved that image; it’s nice to see an example of it in reality

    This made me chuckle. We now know that you’d have to wait an awfully long time to get a clear sky on Venus!

  45. DigitalAxis

    @41 MTU: on the other hand, there are a lot of astronomers who have NEVER considered Pluto to be a real planet. I’m one of them (never mind that I wasn’t alive until after Charon was discovered, which sealed the deal for many)

    Obviously, if you swapped Ganymede and Mercury, Mercury would become a Moon; if you swapped Pluto and Mercury, it’d be Dwarf Planet (albeit a MUCH larger one in size and mass… context DOES matter. 2M1207b is currently considered (as far as I know) a planet, even though 2M1207A is a brown dwarf. Put 2M1207A in a solar system and it’s (just) conceivable we’d call it a planet and 2M1207b a moon.

  46. Nigel Depledge

    Ian S (44) said:

    what is so special about Pluto?

    Erm … it’s been mistaken for a planet for the last 80 years?

  47. Nigel Depledge

    The Messenger pic is very cool, but I’m sure I’ve seen a very nice pic of Earth and Moon taken by a recent space probe that gave a really nice feel for our home planetary system.

    Thinks . . . maybe it was Messenger on a fly-by during its journey to lose enough orbital velocity to get to Mercury?

  48. Nigel Depledge

    Re: Pluto’s status.

    I’m firmly convinced that the IAU (being the international body representing professional astronomers) should be free to define “planet” any way they see fit.

    I do a lot of work in protein science, and if some laypeople came along and tried to tell my profession’s representative body how to define “protein”, I’d be pretty miffed.

  49. astrolabe_cat

    Damn it. That video has me sobbing.

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