Pluto's Small Moons Are Unlike Any Other

[Judi Lynn]

The strange blend of surface chemistry on Nix and Hydra raises big question about the evolution of the Pluto system.

by Kimberly M. S. Cartier
10 December 2024



Pluto’s minor moons Nix (left) and Hydra (right) were discovered in 2005 by the Hubble Space Telescope. Credit: (left) NASA/JHU-APL/SwRI/Roman Tkachenko/Wikimedia Commons, Public Domain; (right) Italyoz484/Wikimedia Commons, CC BY-SA 4.0


The solar system past Neptune is filled with an uncounted number of small, unusual worlds, from barely visible specks of ice to sugar-coated snowmen to Pluto and its five known satellites. These trans-Neptunian objects (TNOs) are the icy leftovers of planet formation and provide a glimpse into the early composition and evolution of the solar system.

Recently, astronomers observed the Pluto system with the James Webb Space Telescope (JWST) and discovered that two of Pluto’s small moons, Nix and Hydra, have surface compositions unlike any TNO studied thus far.

The moons have abundant water like distant dwarf planet Haumea, ammonia like Pluto, and reddish material like Pluto’s major moon, Charon, explained Bryan Holler, a planetary scientist at the Space Telescope Science Institute in Baltimore, Md. This blend of surface chemistry has not been seen anywhere else.

“What is going on here? What is causing these objects to have these surface compositions that are unique in the outer solar system?” he asked. Answering these questions could reveal the mysterious and likely chaotic history of the Pluto system.

More:
https://eos.org/articles/plutos-small-moons-are-unlike-any-other

[love_katz]

1. Those are some weird looking moons.

As always, thank you for the wonderful articles that you share.

[reACTIONary]

4. For weird, how about this.....

Also pictured by New Horizons, further out in the Kieper Belt.

https://en.wikipedia.org/wiki/486958_Arrokoth

[JoseBalow]

10. Looks like a sad snowman

[love_katz]

12. Now that is strange.

Its orbital behavior must be pretty interesting.

[reACTIONary]

13. At the scale of the Solar System its orbital behavior would be determined basically....

.... by its center of mass, not not its shape or attitude, so it would actually be rather standard. However, it seems to be composed of two objects that came together rather slowly, so that process, orbiting each other, so to speak, would have been pretty interesting.

[JohnnyRingo]

2. K&R. Thanx for posting!

I love reading about this stuff.

[SalamanderSleeps]

3. Pluto is still a planet? With moons and everything?

[reACTIONary]

5. And interesting planetary geography...

.... and atmospheric dynamics. It's a "world" if not a planet.

[muriel_volestrangler]

17. 457 minor planets are known or suspected to have moons

https://en.wikipedia.org/wiki/Minor-planet_moon

NASA used this in its test of crashing a probe into the moon of an asteroid to see how much its orbit changed:

With a diameter of about 525 feet (160 meters) – the length of 1.5 football fields – Dimorphos is the smaller of two asteroids in a double-asteroid system. Before DART's impact, Dimorphos orbited the larger asteroid called Didymos (Greek for "twin" ), every 11 hours and 55 minutes.

Neither asteroid poses a threat to our planet, which is one reason why this asteroid system was the ideal place to test asteroid redirection techniques. At the time of DART's impact, the asteroid pair was 6.8 million miles (11 million kilometers) away from Earth as they traveled on their orbit around the Sun.

The DART spacecraft was designed to collide head-on with Dimorphos to alter its orbit, shortening the time it takes the small asteroid to travel around Didymos. Compared with Dimorphos, which has a mass of about 11 billion pounds (five billion kilograms), the DART spacecraft was light. It weighed just 1,210 pounds (550 kilograms) at the time of impact. So how did such a light spacecraft affect the orbit of a relatively massive asteroid?
...
After the DART impact, scientists used a technique called the transit method to see how much the impact changed Dimorphos' orbit. As observed from Earth, the Didymos pair is what’s known as an eclipsing binary, meaning Dimorphos passes in front of and behind Didymos from our view, creating what appears from Earth to be a subtle dip in the combined brightness of the pair. Scientists used ground-based telescopes to measure this change in brightness and calculate how quickly Dimorphos orbits Didymos. By comparing measurements from before and after impact, scientists determined that the orbit of Dimorphos had slowed by 32 minutes to 11 hours and 23 minutes.

https://www.jpl.nasa.gov/edu/resources/teachable-moment/the-science-behind-nasas-first-attempt-at-redirecting-an-asteroid/

(I'd dispute the use of "slowed" there - the orbit of Dimorphos shortened to 11 hours 23 minutes.)

[reACTIONary]

6. Go New Horizons!

[GiqueCee]

7. Fascinating...

... I'd forgotten that Pluto's largest moon was named after Charon, the ferryman to the underworld. A chilling reminder of how Mr. Tombaugh and his contemporaries viewed the solar system's most distant planet. Or is it still just a rock with a weird orbit?

[Solly Mack]

8. You show'em Pluto!

[reACTIONary]

14. FAFO....

[Alice Kramden]

9. Super interesting

Thanks for posting!

[airplaneman]

11. Pluto now that's a Goofy planet. N/T

[SorellaLaBefana]

15. Yes. "Bully for Brontosaurus" and for Pluto too !

Obviously, whatever Pluto is called by some quarrelsome primates who are poisoning their own world has no impact on the astronomical body.

However, this primate's take is that (whilst if discovered today, it would not meet the definition of 'planet') it was considered a planet when it was discovered, and in the hope of building trust and understanding across the generations, a Planet it should remain.

In his book "Bully for Brontosaurus: Reflections in Natural History" Stephen Gould argued for retaining the name Brontosaurus (a name familiar to generations of children and adults) rather than (as it had been at the time) force replacement with the name Apatosaurus (at the time thought to have been the same dinosaur, but described earlier and thus having primacy).

Fortunately, in the case of Brontosaurus I think that it was later determined that Apatosaurus was a distinct creature and Brontosaur was again the accepted name. I may be wrong on this—not being either a paleontologist, or (any longer) a dino-infatuated ten-year old.

Gould's central argument, which also, I believe, applies to Pluto, is that since it is not uncommon for scientific names to be revised (for a variety of reasons) that such name changes applied to publicly well known (and, in the case of Brontosaurus, beloved) things only causes disruption and confusion to the public, whilst not having any recognizable adverse impact on active scientific study and understanding.

Rare exceptions to a general naming convention should be something with which scientists can cope with no more trouble than with which they deal with lumps in their porridge.

I still miss Pasteurella pestis (The Plague bacillus) as well.

Although in this case the change in nomenclature seems quite appropriate, as the organism was discovered by Dr Yersin (who worked for the Pasteur Institute). It was still called P. pestis when I was in medical school in the early 1970s—although it had been renamed Yersinia pestis in 1944.

Change is hard, yet in some situations Not changing can be unjust and make scientific study more difficult.

However, I strongly agree with Dr Gould: Public familiarity and understanding should be considered when making name changes to well known entities only because of narrow naming conventions.

Baby and Bath Water should both be considered.

[eppur_se_muova]

16. Actually, it sounds like they're like lots of others -- all at once ! nt