Meet Metis – Jupiter’s Closest, Quickest Moon

Processed raw image of Metis captured by NASA’s Galileo spacecraft in 1997. (NASA/JPL/Jason Major)

Everyone’s heard of Jupiter’s four most famous moons Europa, Io, Callisto, and Ganymede—we’ve known about them for over 400 years, thanks to Galileo—but giant Jupiter has many more moons than that. To date there are thought to be 69 natural satellites orbiting Jupiter. 53 are officially named, while 16 are awaiting further confirmation. So you’d be forgiven for not being immediately familiar with all of them…it’s a big Jovian family!

The little world seen above is one of Jupiter’s smaller and lesser-known satellites and it holds a particular distinction. It’s called Metis (pronounced like “meet” in the present tense, not “met” in the past) and it’s only about 37 miles across and 21 miles high. It is the closest moon to Jupiter, orbiting within the planet’s main ring (yes, Jupiter has rings) at a distance of about 80,000 miles. It’s also Jupiter’s speediest moon—at 70,500 mph it completes a single orbit in just over 7 hours. That’s almost three hours less than a Jovian day!

The image above was captured by NASA’s Galileo spacecraft on November 6, 1997, two years into its 8 years in orbit at Jupiter. It’s a highly-upscaled version of a raw file I downloaded from NASA’s Planetary Data System (PDS) archive using SETI’s OPUS site. I’ve recently been looking into some raw data from older missions with the goal of processing better versions of things I had worked on in previous years using lower-quality preview JPEGs, and also finding some things I didn’t know about before. Metis is one of them!

Galileo wasn’t the first spacecraft to capture images of Metis; actually Voyager 1 was. The moon was discovered by JPL astronomer Stephen Synnott in data acquired by Voyager 1 in 1979 during its flyby of Jupiter. In March 4 of that year Metis was captured passing in front of Jupiter’s bands of swirling clouds…imagine its view!

The image below is a color-composite I assembled from Voyager 1 observations in red, green, and blue visible-light filters. 37-mile-wide Metis is a tiny speck near the lower right.

Color-composite of Metis and Jupiter from Voyager 1 in March 1979. (NASA/JPL/Jason Major)

Can you spot Metis? If not, here’s some help:

There are three other inner moons of Jupiter in addition to Metis, which is the closest—Adrastea (the smallest and the only other inner moon to orbit faster than a Jovian day), Amalthea (the largest and first-known), and Thebe (rhymes with Phoebe). All orbit between the rings and the orbit of Io, the innermost of the four Galilean moons.

(I processed a Galileo image of Thebe as well:)

Processed raw image of Thebe from Galileo on Jan. 3, 2000. (NASA/JPL/Jason Major)

We don’t know that much about Metis, other than like the other inner moons it’s quite dark (albedo of .06) and is probably made mostly of water ice, based on density.

Learn more about Metis here, and find a full list of Jupiter’s known moons here.

 

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56 Comments

  1. I would have thought that being made mostly of water ice, it would have a high albedo, being MORE reflective, therefore lighter. But 0.06 is very dark. How do we jibe the two statements?

    Liked by 7 people

    1. Jason Major says:

      The inner moons are dark from multiple possible sources: staining from material ejected off Io; material from the rings; and “baking” from radiation exposure between solar UV and Jupiter’s magnetic field.

      Liked by 6 people

    2. SSSBuddy says:

      Ice is relatively transparent, certainly compared to other common substances. So it only takes a bit of impurities to affect the light signature. The reflectivity- at least, in optical wavelengths- is determined by a surprisingly shallow layer of the object.

      The fact that you don’t see it doesn’t mean it’s not there, and that fact that you see it doesn’t mean your eyes are accurate instruments. That’s called naive realism.

      Liked by 5 people

      1. Naive realism? Never heard the term before but that doesn’t mean it doesn’t exist, right? 😉

        Liked by 3 people

  2. olimperio says:

    Reblogged this on Olimpo.

    Liked by 7 people

  3. K.M. Sutton says:

    Such an intersting read! thank you for sharing! ❤

    Liked by 7 people

  4. Great Blog! Thank you!

    Liked by 6 people

  5. milestonemonger says:

    It’s hard to even imagine that speed. You have some awesome content here and keep up the good work!

    Liked by 7 people

  6. The Composer says:

    The scale is baffling..

    Liked by 5 people

  7. Oh this is so cool!!

    Liked by 6 people

  8. Tim Harlow says:

    Thanks for the really wonderful photos.

    Liked by 5 people

  9. arooshidayal says:

    This is really amazing!

    Liked by 6 people

  10. Preeti Mishra says:

    hi

    Liked by 5 people

  11. Astro Josh says:

    “Metis the Messenger” ❤
    Check my blog for some Astronomy articles 😁😁

    Liked by 4 people

  12. jiscience says:

    amazing..very nice information.

    Liked by 4 people

  13. dodysworld says:

    i am so greatful there are people who have the interest and talent to learn of that thing they are interested in, and then they are willing to share their hard work with the rest of us. thank you for your interest and hard work.

    Liked by 4 people

  14. Altynbekova says:

    Good, it’s beauty. Good afternoon friends

    Liked by 4 people

  15. Altynbekova says:

    Good, it’s beauty

    Liked by 4 people

  16. Altynbekova says:

    Good, it’s amazing. Good afternoon mate

    Liked by 5 people

  17. that’s really fast for a messenger!! =) thanks for sharing all the info, very nice read!!

    Liked by 3 people

  18. Interesting & informative.. good 👏👍

    Liked by 3 people

  19. abookloversthoughts says:

    Fascinating!

    Liked by 4 people

  20. Wow…this was so interesting to read!!

    Liked by 3 people

  21. jesser1971 says:

    i thought a solar eclipse between Jupiter and the earth there wouldn’t be any any visible stars in the sky for awhile a planet that size i would think ,heck i dont know

    Liked by 3 people

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  23. thestandpointview says:

    This is awesome and informative. Very interesting read. 👍

    Liked by 1 person

  24. CC says:

    So cool!

    Like

  25. rajlakshmihb says:

    That was a fascinating read. 😀

    Like

  26. PETWONE says:

    That’s pretty cool!

    Like

  27. etiliyle says:

    So interesting

    Like

  28. This was such an interesting read.

    Like

  29. Reyna Hurand says:

    Fascinating read! Thank you for sharing.

    Like

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  31. 69 moons? Wow I had no idea

    Like

  32. Jatin Bedi says:

    Thanks for the info, i really appreciate, i didn’t know about this all.

    Like

  33. @pencified says:

    Great post ! Informative

    Liked by 1 person

  34. Laveena says:

    Soo exciting! I had no idea Jupiter had soo many moons

    Liked by 1 person

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  36. tudornpana says:

    Very interesting

    Liked by 2 people

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