The DownlinkApr 19, 2024

Scratching the surface

Space Snapshot

Hirise mars crater ice

If you want to find ice on Mars, you may just have to scratch (or impact) the surface. Images like this one, from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter, show impact craters on the Martian surface that have exposed water ice hiding beneath the regolith. The ice doesn’t stick around forever, though; it will gradually sublimate from solid to gas because of Mars’ low atmospheric pressure. Image credit: NASA/JPL-Caltech/University of Arizona.

Fact Worth Sharing

Mars illustration

Snow sometimes falls on Mars in the form of water ice, but with low temperatures and a thin atmosphere, it sublimates into a gas before it even touches the ground. Carbon dioxide snow, or dry ice, is much more likely to reach the ground.

Mission Briefings

Pluto enhanced color
Solar System

The key to Pluto’s heart may also dash hopes of a subsurface ocean. The giant heart-shaped feature on Pluto’s surface has been a mystery since it was first observed by NASA’s New Horizons spacecraft in 2015. But an international team of astrophysicists has used simulations to reproduce the feature, attributing it to a giant and slow oblique-angle impact in Pluto’s early history. The team's findings also suggest that there is no ocean under Pluto’s icy surface. Pictured: Pluto in enhanced color, based on images collected by New Horizons. Image credit: NASA / JHUAPL / SwRI.


NASA has confirmed the Dragonfly mission to Titan. The rotorcraft has been approved to progress to the completion of its final design, followed by the construction and testing of the entire spacecraft and science instruments. Dragonfly is targeted to arrive at Saturn’s moon Titan as soon as 2034.


NASA has made a plea for suggestions to save Mars Sample Return. This week the agency announced that its current architecture for returning samples from Mars is untenable with its current budget. In an unprecedented move, NASA issued a call to industry, JPL, and NASA centers for new ideas on how to get the samples now being collected by the Perseverance rover back to Earth in an affordable, timely manner. The Planetary Society released a statement in response to the updated plan.


ESA is reviving ExoMars. This week, the European Space Agency awarded a contract to a consortium of companies to resume work on the ExoMars mission, including the Rosalind Franklin rover. The overall ExoMars mission was derailed in 2022 when cooperation with the Russian space agency Roscosmos was suspended because of Russia’s invasion of Ukraine.

From The Planetary Society

Exoplanet K2 18b
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Are there other watery worlds out there? Amaury Triaud, an astronomer from the University of Birmingham in the U.K., joins this week’s Planetary Radio to talk about a new method for potentially detecting liquid water on the surfaces of terrestrial exoplanets. Plus, you’ll hear more about "The Lost Universe," NASA's first tabletop role-playing game.

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Space science costs money. Here’s why it’s worth it. To study space, we have to employ scientists, build observatories and research facilities, and launch spacecraft — among other expensive things. But these investments pay off in many ways, from the inherent value of better understanding the natural Universe in which we live to more pragmatic benefits like economic growth. Learn more about why space science is worth the money and how you can advocate in support of it.

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Have you contemplated attending a Planetary Society event? Our recap of Eclipse-O-Rama 2024 might be what convinces you to attend one in the future. Read about our awesome eclipse festival, including first-hand accounts from members who joined us in Texas to take in this marvel of nature.

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We’re going beyond the horizon. Will you join us? As a supporter of The Planetary Society, you know that every success in space exploration results from the community of space enthusiasts, like you, who believe it is important. That's why we're looking for you to help us raise vital funds to expand our core mission and strengthen the Society. Your gift of any amount today is an investment in the future and will help us usher in the next great era of space exploration.

What's Up

Jupiter illustration

In the early evening, look for very bright Jupiter in the west. Reddish Mars and yellowish Saturn shine in the pre-dawn east, low to the horizon. The Lyrid meteor shower peaks overnight between April 21-22, with meteors the night before and after as well. Find out what else April’s night skies have in store.

Commemorate your eclipse experience

Eclipse necklace

The 2024 total solar eclipse left a big impression on those who experienced it. To help hold onto those memories forever, pick up some commemorative merch. Our partners at Chop Shop have an array of special eclipse apparel, jewelry, mugs, posters, and more to commemorate the 2024 total solar eclipse. Check out the collection today.

Wow of the Week

Merc europa clipper

The Planetary Society’s visual storyteller Merc Boyan visited the Jet Propulsion Laboratory this month to see the Europa Clipper spacecraft in the clean room getting ready for its October launch. Europa Clipper will arrive at the Jupiter system in 2030 to study the moon and learn more about what lies beneath its icy crust. You’ll be able to see more from Merc’s JPL visit in an upcoming video, so keep an eye on our YouTube channel for its release.

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!