Missions to the Moon, and Methone

Thank you to everyone who signed up to receive this newsletter before I wrote a word of it. I plan to use this space to highlight my recent work, promote the work of my friends in space science and journalism, and talk about the countless worlds of the solar system that aren’t planets.

For my first newsletter, I’m featuring Saturn’s moon Methone. When Cassini flew past it at a distance of under 5,000 kilometers a decade ago (21 May 2012), the images revealed a world that looked like an egg. Read to the end of this newsletter to learn more about Methone!

News: Artemis I, Orion, SpaceX, lunar missions

I can’t be a one-stop shop for space news – there are lots of space newsy websites who will do it way better – but I can highlight good recent work by some of my favorite writers.

• Alex Witze has been a mentor and friend in space science newsrooms ever since I started writing, and is my guide to journalistic principles. I always go to her first for straight news coverage of politically fraught topics in space exploration. Here is her fact-filled post-launch report on the Artemis I launch for Nature.

• I also know a lot of great feature writers. Nadia Drake is terrific at balancing reporting with lyrical prose, like in her background feature for Scientific American on the Artemis I launch, with its “promise that, at least in spaceflight, the U.S. remains exceptional, with capabilities, ambitions and achievements as yet unsurpassed.”

• Shannon Stirone excels at meaty coverage of the messy, human, political, and social, and emotional side of space stories. Here’s her writeup for the New York Times opinion page of a roundtable discussion she moderated with Lori Garver, David Grinspoon, and Leroy Chiao, about “why Artemis and NASA’s push to the Moon feels not quite right.”

• And if you don’t have time to read a feature, here is a super informative, bullet-point article by Miriam Kramer and Alison Snyder for Axios on Elon Musk’s growing geopolitical power.

Ten cubesats launched with Artemis I toward the Moon. Doug Messier at Parabolic Arc has a page keeping track of their status. As I write this post, Doug’s latest update was yesterday, when six were reportedly operating as expected (ArgoMoon, BioSentinel, CuSP, EQUULEUS, LunaH-Map, and Lunar IceCube). Sadly, no signal has been received from the NEA Scout solar sail asteroid flyby mission, and the JAXA lunar lander OMOTENASHI was tumbling.

More spacecraft are headed toward the Moon already or soon:

• A Japanese private company, ispace, expects to launch its HAKUTO-R M1 lander with the UAE’s Rashid 1 rover on or after 28 November for an April landing. (Official website – official Insta – background story from Space News)

• The long-delayed Lunar Flashlight is piggybacking on the HAKUTO-R launch. The wonderful Barbara Cohen is project scientist for this mission, which will use near-infrared lasers to map water ice near the lunar south pole, looking for resources for future human exploration.

• The tech demonstration mission CAPSTONE is now settling in to a near-rectilinear halo orbit after a navigational scare last month. (RocketLab page – NASA page)

• Danuri (also known as the Korea Pathfinder Lunar Orbiter) should enter lunar orbit in mid-December; if successful, it’ll be South Korea’s first mission beyond Earth orbit.

Emily’s Space Craft

This time of year, my main focus is my Etsy store. I select naturally colored gemstone beads to match the colors, brightnesses, and comparative sizes of the worlds of the solar system and beyond, creating jewelry, sculptures, and other art. It’s mostly geekier than you might think. I download data from JPL Horizons on sizes and distances to different worlds to build huge spreadsheets that inform my solar system tree sculptures. I calculate proportions for bead sizes and necklace lengths so I can make things like this necklace featuring correct proportional sizes and separations of Pluto and Charon. I’ve researched color and albedo to make sure the stones I pick are at least (as they say in the movies) “inspired by” the correct shades, and I take inspiration from stones and findings for unique pieces representing planets, moons, and comets. I’ve made jewelry inspired by the Hertzsprung-Russell diagram and resistor color codes used in electronics.

Special for newsletter subscribers: Use the code EMILYNEWS for $10 off anything in the shop, or EMILYNEWS25 for $25 off any order totaling $200 or more! Both of these offers end on 1 December.

Watch My Talk!

I’m really proud of the talk I gave to the Division for Planetary Sciences meeting in Canada last month. I was invited to speak on the topic of the history of planetary exploration. It was a comically broad topic, but I found a path forward. You can watch it or read the transcript here. I felt a little out of practice speaking to a crowd, but I think it went pretty well, and I really pleased at the number of people who complimented me on it afterward.

My Stuff Around the Web

Blog entries and articles by me in the last month. I blog at Patreon; all my posts are public, and I deeply thank my Patrons for supporting me in doing that work. Please consider joining them!

• Was Interstellar Object `Oumuamua a Chunk of Exo-Pluto? The interstellar pancake named 'Oumuamua might have been a chip off a Pluto-like object in another star system (for Sky & Tel, 15 Nov)

• I Read That Journal Article About Hipparchus’ Lost Star Catalog So You Don’t Have To In which I figure out exactly what the claim is around what was described as the oldest star catalog (blog, 31 Oct)

• Cognitive Behavioral Therapy Work I’m doing to develop successful coping strategies for my ADHD (blog, 18 Oct)

• Amateur Finds New Images of Uranus’ Rings in 35-Year-Old Data: A space image processing enthusiast, Ian Regan, found new science in old Voyager data. Ian was kind enough to share processing details with me, which I posted in the article (for Sky & Tel, 20 Oct)

• DART Asteroid Redirect Test Wildly Successful: They needed to shorten the moon’s orbit by 73 seconds. They shortened it by more than half an hour (for Sky & Tel, 11 Oct). See also my previous DART stories about the launch, impact day, and ground-based imaging of the impact.

More About Methone

Methone, which was first discovered in Cassini images, is a ringmoon, a regular moon that formed within Saturn’s ring plane. Methone orbits between the G and E rings, between Mimas and Enceladus, and is in a 15:14 orbital resonance with Mimas (so Methone goes around Saturn 14 times for every 15 times that Mimas does). It was first discovered in Cassini images. It’s tiny, only 3 kilometers across (to be precise: 3.8x2.6x2.4 km), so by all rights it should be a lumpy thing. So its egg shape was a big surprise! That was the only Cassini encounter with Methone, but it was a good one, yielding lots of science.

The egg shape, technically called an ellipsoid, indicates that it’s a loose pile of material, held together by self-gravity, but stretched out by its spin. From that, Peter Thomas and coworkers calculated its mass and therefore its density: only 1/3 that of water ice. It has to be at least 2/3 empty space, similar to the density of windblown, compacted snow. The extreme smoothness suggests that craters get erased really fast, so it’s not surprising that it orbits within an arc of ring material, stuff that probably got knocked off the surface by little impacts. Its color also indicates a fresh surface: it’s spectrally fairly gray, reflecting only a little more strongly in infrared than ultraviolet wavelengths (IR3/UV3 ratio of 1.17), like the mid-sized icy moons of Saturn, not red, like the inner ringmoons. It has a relatively dark surface for a Saturnian moon, reflecting 42% of the visible light that strikes it. I’d represent it in art with a warm, mid-gray tone.

The best source for information on Methone is a chapter in the 2018 book Enceladus and the Icy Moons of Saturn on “The Inner Small Satellites of Saturn, and Hyperion,” by Peter Thomas, Matt Tiscareno, and Paul Helfenstein. This Hedman et al. (2020) ApJ article has some updates. Here are Cassini’s best images, the Wikipedia Methone (moon) page, and a literature search for Methone information.

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