The DownlinkApr 21, 2023

Rocket flight and the five dwarfs

Space Snapshot

Pluto snakeskin terrain

When the New Horizons spacecraft flew by Pluto in 2015 it saw the strange surface features pictured here, which scientists have nicknamed “snakeskin terrain.” The series of ridges is unlike anything we’d seen before, and is not yet fully understood. Pluto is one of the Solar System’s five official dwarf planets, all of which are fascinating worlds that have yet to be fully explored. Image credit: NASA/JHUAPL/SwRI.

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Fact Worth Sharing

Pluto illustration

The dwarf planet Eris was named after the Greek goddess of discord and strife, which is fitting; discoveries about Eris were instrumental in the eventual reclassification of Pluto as a dwarf planet, which sparked a lot of discord and strife among the public.

Mission Briefings

Juice launch

ESA’s Juice mission is on its way to Jupiter’s icy moons. The spacecraft took off from French Guiana on April 14, beginning an eight-year journey to Jupiter, where it will study the moons Europa, Callisto, and Ganymede. En route, the spacecraft will perform the first-ever Earth-Moon dual gravity assist flybys in August 2024, followed by a Venus flyby and then two more Earth flybys before reaching Jupiter in 2031.

small bodies

China has selected an asteroid for a deflection test. At last week’s biennial Planetary Defense Conference, a representative of the mission announced that the near-Earth object 2019 VL5 will be the target of a dual-spacecraft asteroid deflection and observation test, due to launch in 2025. An impactor spacecraft will smash into the roughly 30-meter (100-foot) asteroid to attempt to alter its velocity. Another spacecraft will observe the impact and evaluate its effect on the asteroid.


Planetary Society board member Britney Schmidt’s work has a big influence here on Earth. As a planetary scientist, Schmidt does research in Antarctica where conditions are analogous to frozen deserts on worlds like Mars. Time Magazine named Schmidt one of the 100 most influential people of 2023 because of her research on an enormous glacier that is melting due to climate change.


SpaceX’s Starship exploded during its first orbital test flight. The company’s Super Heavy booster and Starship spacecraft lifted off on April 20 from the Starbase launch facilities in Boca Chica, Texas, but self-destructed several minutes after taking off in what SpaceX described as a "rapid unscheduled disassembly." The test still represents a step forward in the company's ambitions to send humans to the Moon and Mars aboard Starship.

From The Planetary Society

Mars retrograde
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Mercury is now in retrograde. What does that really mean? The Solar System’s innermost planet has entered a period of apparent retrograde motion, meaning its path across our night sky has reversed direction. This is a regular and well-understood phenomenon, although pop-culture references to the planet’s periods in retrograde tend to miss the mark. Get the facts about Mercury in retrograde and why planets seem to go backwards at times. Pictured: A map of Mars’ apparent retrograde motion, which happens for a similar reason. Image credit: Tomruen/Wikimedia commons.

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Our Digital Day of Action was a great success. Members and supporters from nearly every state took a total of more than 1,500 advocacy actions in support of space science and exploration, including writing Congress to help save the VERITAS mission to Venus. If you missed it, don’t worry; you can still take part. Take a look at our advocacy toolkit with information about what we’re advocating for and actions you can take right now from home no matter where you live.

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If you could visit 10 places in the Universe, which would you choose? Science communicator Phil Plait, also known as the Bad Astronomer, made his picks for his new book, “Under Alien Skies: A Sightseer’s Guide to the Galaxy.” Plait takes readers on an imaginary journey to 10 strange and beautiful places, describing what visitors would witness if they could be there themselves. Plait joins this week’s Planetary Radio to talk about the journey we all wish we could really take.

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Join us at the Humans to Mars Summit. Explore Mars' Humans to Mars Summit is coming up, and tickets are now available. The annual conference brings experts from around the world together in Washington, D.C., to discuss the effort to get human explorers to Mars. Hear from former Planetary Radio host Mat Kaplan, along with scientists, engineers, astronauts, space agency leaders, and many more. Learn more.

What's Up

Meteors illustration

The Lyrid meteor shower peaks this weekend, on the nights between April 21 and 23. While you’re out spotting meteors in the evening, take a look at Venus in the west, with Mars higher above it. If you stay up meteor-watching all night, you’ll get to see Saturn in the predawn eastern sky. Find out what else to look for in April’s night skies.

Wow of the Week

Pluto globe printable

Want to have the most famous dwarf planet for yourself? You can make your own Pluto globe using this printable model. While working at the University of Arizona’s Lunar and Planetary Laboratory, planetary scientist Sarah Morrison created this Pluto globe using a photomosaic from New Horizons image data. Read her directions for how to make the globe. Image credit: NASA/JHUAPL/SwRI/Sarah J. Morrison.

Send us your artwork!

We love to feature space artwork in the Downlink. If you create any kind of space-related art, we invite you to send it to us by replying to any Downlink email or writing to [email protected]. Please let us know in your email if you’re a Planetary Society member!