Sarah Hörst
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planetdr.bsky.social
Sarah Hörst
@planetdr.bsky.social
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Professor of planetary science at Johns Hopkins. Titan’s biggest fan. Pomeranian wrangler. Runner. Love many, trust few, always paddle your own canoe. She/her. sarahhorst.com
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planetdr.bsky.social
A small love letter to Baltimore:

This morning I drove by a giant pile of snow that had a sign stuck in the top that said Yes snow, no ICE.

Then I saw a makeshift know your rights/whistles/zines distribution device.
A Tupperware full of zines and whistles attached to a pole with know your rights posters
February 6, 2026 at 2:58 PM
planetdr.bsky.social
I love this Dragonfly tradition
Picture of a certificate of appreciation for me. It says “CERTIFICATE oF APPRECIATION awarded to Sarah Hörst - for her inspiration, support of teamwork, steadfast devotion to science and for putting things in the chat we all were thinking but maybe not brave enough to say seal of DRAGONFLY 2025 DRAGONFLY ANNUAL TEAM MEETING”
February 5, 2026 at 5:29 PM
planetdr.bsky.social
Still snowing. Still have power. Now have coffee cake.

All 4 dogs and my husband are napping.
Coffee cake on a white plate with some gooey frosting on it.
January 25, 2026 at 5:04 PM
planetdr.bsky.social
A little hard to tell because it’s blown around a bit but it looks like we’ve gotten about 4” in Monkton, MD. Coming down pretty hard now.
View of a snow covered yard. There’s fence and a few bushes. Lots of trees in the background
January 25, 2026 at 12:31 PM
planetdr.bsky.social
Yeah this is not great.
Screenshot of Apple weather predicting 23-29 inches of snow
January 21, 2026 at 3:27 PM
planetdr.bsky.social
Looking promising here in northern Maryland
Trees with dark sky with some hints of greens and pinks starting to form
January 19, 2026 at 11:14 PM
planetdr.bsky.social
Sure.
Bear asleep on on a gray leather couch Gizmo sitting in bed surrounded by pillows Gizmo and bear sitting on a small humans lap. The small human is mostly cropped out because small human.
January 14, 2026 at 12:41 AM
planetdr.bsky.social
They are Chesapeake bay retrievers (moose and Kimber). I should post them more they are good beans
Kimber and moose in their crate ready for sleepies
January 7, 2026 at 4:53 AM
planetdr.bsky.social
This section from the wikipedia article has killed me dead
^ Scientific reaction The Impact mini-series received little comment from the scientific community due to its lack of realism, incorrect use of terminology, and basic misunderstanding of the law of gravity
January 3, 2026 at 3:19 AM
planetdr.bsky.social
Pretty normal
Bear and gizmo sitting on the couch. Gizmo is snuggled up in a fuzzy gray blanket.
December 30, 2025 at 5:05 PM
planetdr.bsky.social
Thrilled that peanut butter has finally entered the chat and it had a nice texture too. Probably tied for my favorite so far.
Gold circle container with a wavy gold pattern on it. Black circle paper that says PEANUT BUTTER NOUGAT DRAGÉES by Melissa Coppel Melissa Coppel Chocolatier Three small Brown spheres that are dusted with brown powder Zoom in of the chocolate. This is Amalthea. Another gray space potato. It does have some albedo variations and some craters. If it was a color image it would appear reddish due to sulfur compounds from Io. This is one of the many reasons we do not eat actual moons.
December 20, 2025 at 12:24 AM
planetdr.bsky.social
Tonight was Amalthea. Tonight was also when I discovered my brain has been rearranging the letters in Amalthea ever since I knew it existed.
DECEMBER 19| AMALTHEA (JUPITER) Amalthea is a highly unusual inner moon of Jupiter, nestled close to the huge planet (181,000 kilometers away), within its intense radiation belt. An irregular world, and the reddest object in our solar system, she glows faintly against the gas giant's brilliance. Amalthea radiates more heat than she gets from the Sun, likely due to Jupiter's nearby influence, With Thebe, this moon helps sustain Jupiter's main ring system, supplying dust from micrometeorite impacts. Amalthea was discovered in 1892 by American astronomer Edward Emerson Barnard, using the 36-inch refracting telescope at California's Lick Observatory. Barnard spotted Amalthea via the telescope's eyepiece, not photography or digital imaging. She was the last moon of any planet discovered this way; a significant moment in astronomy, as no new moons of Jupiter had been discovered in nearly three centuries. Named for a naiad who nursed the infant Jupiter with goat's milk, Amalthea is depicted as a goat, symbolizing nurturing. Tiny and enigmatic, she plays a key role in nurturing and shaping Jupiter's inner environment. A NOTE FROM LINA Amalthea is a female mythological figure. I chose to represent the goat using a technique that breaks the image into organically flowing shapes. At first glance, the form is unclear — you see merely a shimmering pattern. Only when you move closer does the image begin to emerge. The form reveals itself slowly, sometimes only partially — always a bit of a mystery. The technique is the same one I used in the Xitan Hotel project, created with Posca gold markers and white, swirling organic lines.
December 20, 2025 at 12:21 AM
planetdr.bsky.social
Thebe is the 1st moon on this adventure that I knew nothing about. Turns out it’s tiny and mostly crater?

This was our 2nd brittle and 2nd gingerbread. It was definitely the better of the three, though still missing the “am I going to have to call a dentist” vibe I associate w/ brittle
Red circle box with a pattern that looks like a flower. Black circle paper that says TOASTED GINGER BREAD TOFFEE BRITTLE by Christine Doerr Neo Cocoa Confections and a few angular pieces of kinda lumpy chocolate Zoom in of the chocolate Grainy picture of actual Thebe with a giant hole (crater) in the middle
December 20, 2025 at 12:15 AM
planetdr.bsky.social
We actually did Thebe yesterday but I was too tired to post about it.

We’ve left the Saturnian system for the Jovian system (by now you’ve hopefully noticed that the moons aren’t actually in orbital order for each system as I initially thought. No idea what the order is!)
DECEMBER 18 | THEBE (JUPITER) Approaching Jupiter's realm, we find numerous moons — ninery-five counted as of March 2025! Thebe, named after a consort to Zeus (Roman myth's Jupiter), is a small, reddish moon orbiting merely 222,000 kilometers from the gas giant planet — closer than Earth to her Moon. Thebe is battered and irregularly shaped, her orbir influenced by Jupiter's titanic presence. She helps contribute material to Jupiter's faint Thebe Gossamer Ring, a ghostly halo of dust which is part of Jupiter's gossamer ring system - a set of tenuous, translucent rings barely visible except in special lighting conditions like backscattered sunlight. The Thebe Gossamer Ring is caused by micrometeorite impacts ejecting into space fine dust particles which spread out along Thebe's orbit due to Jupiter's gravity and magnetic field. Unlike Saturn's icy moons, Thebe is rocky and darker, with a surface similar to asteroids. Though small and dim, Thebe plays an important role in Jupiter's dynamic ring system. A NOTE FROM LINA This moon is one of the smallest in our solar system, with a strange, Lumpy shape. I initially tried to draw it, but the result felt awkward - almost unpleasant. So instead, I shifted my focus to the atmosphere around it. The moon is trapped within Jupiter's rings, and I found that setting far more visually inspiring. Rather than depicting the moon itself, I used its astronomical context as a starting point to create something more abstract and beautiful — an ornament that fits within the collection's overall visual language.
December 20, 2025 at 12:10 AM
planetdr.bsky.social
So here’s the thing. By now we know the chocolates just have no relation to the moons.

But….the chocolate for one of the least cratered moons in the solar system is covered in spots?!?

(It was pretty delicious)
Gold circle container with a gold man’s face. Black circle paper that says HAZELNUT CARAMEL BONBON by Christopher Elbow Christopher Elbow Chocolates Circle chocolate with pinkish (?) dots all over it Zoom In of the Chocolate. I guess the dots are tan not pink Actually titan. No dots. This is the atmosphere of course but since it is the only moon with a substantial Atmosphere it seemed wrong to pic an image of the surface.
December 19, 2025 at 3:21 AM
planetdr.bsky.social
I wasn’t feeling well last night so we missed…TITAN!
DECEMBER 17 | TITAN (SATURN) During the Cassini space mission which orbited Saturn for thirteen years, the first and only outer solar system landing was achieved when the robotic Huygens probe was deployed from Cassini, and touched down on Titan — a giant accomplishment resulting in many groundbreaking discoveries. As Saturn's largest moon (larger than the planet Mercury). Titan is our solar system's only moon with a dense atmosphere: fifty percent thicker than Earth's, and composed mostly of nitrogen and methane. You wouldn't need a pressure suit to walk on Titan; just a protective spacesuit with oxygen and warmth. Temperatures are about -179 °C (-290 °F) — so cold, methane behaves like water. It even rains on Titan, forming rivers and seasonal weather cycles, making it the only other world in our solar system known to have stable liquids on its surface. To learn more about this unique moon, NASA is set to send nuclear-powered robotic rotorcraft Dragonfly to Titan in 2028, expected to arrive in 2034. A NOTE FROM LINA This moon is named after a Titan — a giant from mythology. Like Phoebe, it draws from the same mythological lineage. For this piece, I chose to depict a male face, inspired by the classical features seen in Greek sculpture — similar to representations of Zeus. The face isn't meant to be a specific figure, but rather a symbolic embodiment of the masculine ideal. I used the same ornamental swirls as in Phoebe, creating a visual dialogue between the two. In the box, they are positioned facing one other, forming a complementary pair - male and female — united by myth, form, and style.
December 19, 2025 at 2:43 AM
planetdr.bsky.social
Daphnis is also a space ravioli.

This chocolate was snickerdoodle, which is again a flavor I don’t associate with chocolate. However this was delicious and definitely my favorite chocolate so far. The texture is really hard to describe it was both crunchy and creamy? Very pleasing.
Black circle container with a white streaky pattern. A circle chocolate with purple/pink/white pattern that looks kinda like a nebula. Black circle paper that says SNICKERDOODLE BONBON by Kate Weiser Kate Weiser Chocolate Zoom in on the chocolate Cassini image of pan inside the keeler gap. It looks like a cross between a spaceship and a ravioli
December 17, 2025 at 12:28 AM
planetdr.bsky.social
Tonight is another shepherd moon: Daphnis
DECEMBER 16 | DAPHNIS (SATURN) Even smaller than Pan, Daphnis dances in the Keeler Gap, a 42-kilometer-wide gap in Saturn's A ring. Though miniature (only 5 miles in diameter, less than the size of San Francisco), her gravitational pull affects ring particles hundreds of kilometers away, stirring waves in Saturn's rings like ripples on a frozen pond. Depending on how Daphnis is tilted during orbit, the moon creates both vertical and horizontal ring ripples, causing a wobbled or sculpted look. Daphnis is named after a shepherd from Greek mythology — appropriate, since she's a shepherd moon keeping the Keeler Gap clear. A NOTE FROM LINA For this moon, I was inspired by incredible NASA photos — this moon isn't round like most others, but small and lumpy, traveling within the rings of Saturn. I found it fascinating to see a moon that breaks the usual expectations of shape. Despite its irregular form, I used a classical round moon shape in the ornament to maintain visual continuity. I applied the same textured line technique I used on the box cover — my "spaghetti" style — to evoke the patterns of Saturn's rings. Within these flowing lines, 1 placed the small moon, echoing the NASA imagery of it nestled in the gap between the rings.
December 17, 2025 at 12:24 AM
planetdr.bsky.social
Pan, as is tradition with Saturn’s shepherd moons is actually a space ravioli and therefore has nothing to do with chocolate. But here we are.

The chocolate was ok. I don’t really associate cranberry with chocolate and this did not change my mind
Red circle box with a red and gold and dark red pattern. A paper circle that says CHICAGO SUNRISE by Katherine Duncan Katherine Anne Confections. And a square chocolate with a dried cranberry stuck to the corner Zoom In of the chocolate An image of the actual pan. Which. Looks like a space ravioli
December 17, 2025 at 12:21 AM
planetdr.bsky.social
I got behind again. Yesterday was Pan
DECEMBER 15 | PAN (SATURN) Discovered in 1990, tiny Pan sails within Saturn's A ring, carving a narrow path in the 325-kilometer-wide Encke Gap in the ring. It acts as a shepherd moon, herding and clearing out particles as it orbits, while its gravity creates visible wave patterns in the nearby ring material — ripples you can see in Cassini photos. Before the Cassini spacecraft visited, Pan was merely a pixelated abstract shape in previous photos. Now, we know Pan is one of the oddest-shaped moons in our system — like a flying saucer or cosmic ravioli — due to a bulging equatorial ridge likely formed as Pan slowly accumulated particles from Saturn's ring. Pan was named in 1991 by the International Astronomical Union (LAU), in keeping with the tradition of naming Saturn's moons after figures from Greco-Roman mythology. Since. Pan was the Greek half-man, half-goat deity of shepherds, Aocks, and nature, the moon's name aligns with its role as a "shepherd moon" in Saturn's system. A NOTE FROM LINA For this piece, I drew from symbols associated with Pan - the mythical goat-man — but chose not to focus on his literal form. Instead, I worked with his symbolic elements: the shepherd's walking stick, which has a beautiful, organic curl that connected naturally with the rest of the ornaments. The red tones are used purely for aesthetic purposes. They tie into the recurring red theme found in many of the other ornaments, adding visual unity while making the piece feel intriguing, rich, and beautiful.
December 17, 2025 at 12:18 AM
planetdr.bsky.social
Hey AGU folks! I’m not at AGU but we’ve got a gaggle of undergrads (they call themselves the vfoxen)presenting the work they did this past summer and fall on VfOx- the oxygen fugacity sensor they are building to send to Venus on DAVINCI. Go check out their poster!
Picture of 7 students standing in front of poster 2294 in the AGU poster hall. The poster title is readable and says Development & Optimization of the Venus Oxygen Fugacity Sensor
December 15, 2025 at 4:58 PM
planetdr.bsky.social
This was probably my favorite chocolate so far (raspberry brownie) despite the fact that Enceladus isn’t raspberry. I like how the blueish hue reminds me of encleadus’ highly reflective icy surface
Gold circle box with stripey wavy things. Black paper circle that says RASPBERRY BROWNIE by Lisa Shoenbeck Good Good Chocolates Half sphere chocolate with a light shiny blue powder Zoom in of chocolate Plumes shooting out of the South Pole of Enceladus
December 15, 2025 at 12:47 AM
planetdr.bsky.social
Then to catch up tonight’s actual moon/chocolate was Enceladus!
DECEMBER 14 | ENCELADUS (SATURN) Enceladus (Greck giant, and a son of Uranus and Gaia), is one of the most active worlds in our solar system. Despite its small size (smaller chan England), it's a prime target in the search for extraterrestrial life. Enceladus astonishes with cryovolcanoes erupting from long fractures, referred to as "tiger stripes" for their distinct appearance. The freezing geysers shoot plumes of water vapor, ice particles, and organic compounds from the moon's south pole. The Cassini spacecraft few through the plumes in 2005 and detected water vapor, hydrogen gas, and organic molecules, including complex carbon-based compounds. Some of this material escapes into space and helps form Saturn's E ring. Bencath the crust lies an ocean, bubbling with seafloor hydrothermal activity, similar to Earth's deep-sea vents, suggesting complex organic chemistry. This dynamic subsurface ocean makes Enceladus a strong candidate for microbial life. The most refective body in our solar system, Enceladus sparkles like an ornament; its bright ice reflects almost all the sunlight it receives — even more than freshly fallen snow. A NOTE FROM LINA This piece was inspired by the Enceladus' surface, which is covered in ice. Its south pole is marked by large canyons and vein-like lines -fractures in the ice that create a striking visual pattern. To capture both the texture and structure of these icy formations, I used layered white ornamental forms to suggest flowing lines ofice. These decorations also appear on the box cover, creating a visual connection and maintaining stylistic continuity across
December 15, 2025 at 12:40 AM
planetdr.bsky.social
The chocolate was both coconut and pistachio so I didn’t even bother. My husband said it didn’t taste strongly of either
Red circle container with a gold pattern that had a smaller circle (like Mimas). Black circle paper COCONUT SUGAR PISTACHIO CARAMEL by Tyler Geertsen Ticket Chocolate The Chicago is square-ish with some white stuff at one corner Zoom in of the chocolate Mimas the moon. Gray and heavily cratered with a ginormous crater that makes it look like the Death Star
December 15, 2025 at 12:36 AM
planetdr.bsky.social
Didn’t feel up to sharing last night but it was night 13 and the Death Star. I mean Mimas.
DECEMBER 13 | MIMAS (SATURN) Mimas, instantly recognizable with its massive impact crater, called Herschel Crater, looks uncannily like the Death Star — though that is purely coincidental, since Star Wars came out before we had good images of this moon. If the Herschel impact had been any stronger, Mimas might have shattered. It's a quiet, relatively small sphere, made mostly of water ice, with very low density, something like a giant frozen snowball; Mimas has recorded some of the coldest daytime surface temperatures of any Saturnian moon - as low as -200°C (-328 °F). A NOTE FROM LINA This was a bit of a challenge; I didn't choose the mythological creatures, because they are giants with snake legs, which did not look so nice. I was looking at the moon itself, and it is one of the moons with the most craters in the whole solar system. It has one very large crater, and because of the crater's size, some scientists refer to this as the "Death Star Moon." I used the "spaghetti" style to mimic the craters and then created the crater with this same technique.
December 15, 2025 at 12:32 AM