The DownlinkJan 29, 2021

A Martian smile and an Apollo anniversary

Space Snapshot

Hirise smile

Mars is happy that we’re coming to visit! Or at least, it certainly looks that way. This recent image from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter shows the Happy Face Crater (named for obvious reasons). HiRISE took an image of the same landform in 2011, and scientists can compare the two images to understand annual changes in polar frost and longer-term climate trends on Mars.

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Fact Worth Sharing

Mars illustration

The Mars Reconnaissance Orbiter is one of the hardest-working spacecraft out there. As well as conducting science and taking stunning high-resolution images, it plays a key role in choosing safe landing sites for other missions like the Perseverance rover.

Mission Briefings

TOI 178 system

The world’s exoplanet missions continue to reveal a diversity of other worlds. First up: NASA’s TESS and the European Space Agency’s CHEOPS discovered a solar system with 5 planets locked in a rhythmic dance that makes them all align at regular intervals. In other exoplanet news, we now know more about the TRAPPIST-1 star system, which has at least 3 planets that could harbor liquid water on their surfaces. New research reveals they are slightly less dense than Earth, which means they are made from a different ratio of materials than our own planet. Pictured: The TOI-178 planetary system discovered by CHEOPS. Image credit: ESA.


NASA’s MESSENGER Mercury mission, which ended in 2015, is still helping us understand how planets evolve. The smaller the world, the faster it cools, contracts, and becomes geologically inactive—at least, that’s the theory. A new paper using MESSENGER data shows Mercury hasn’t contracted as much as we thought, which could help scientists explain how smaller worlds hold on to their interior heat. The key may be thick surface regolith of heavily fractured crust—essentially, insulating planetary blankets.


NASA’s OSIRIS-REx spacecraft will leave asteroid Bennu for Earth on 10 May 2021. The probe, which successfully collected a sample from Bennu last year, will arrive back on Earth in 2023. Before OSIRIS-REx leaves, it may make one last Bennu flyby in April to see how the sample collection site changed after getting high-fived by the spacecraft.


Astronauts completed a spacewalk outside the International Space Station to upgrade the European Space Agency’s Columbus module. The upgrades included a new antenna that will enable high-speed data links between the station and the ground, enabling greater science return. Another spacewalk is planned for next week.

From The Planetary Society

Oumuamua ESO impression
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Could ‘Oumuamua be an alien artifact? Probably not, but distinguished Harvard astrophysicist Avi Loeb is claiming a controversial hypothesis that ‘Oumuamua, the first object shown to have originated outside our solar system, could be a light sail built by an alien civilization. This unique object was discovered in 2017 by the Pan-STARRS 1 telescope in Hawai`i, and seems to be a dark red highly-elongated metallic or rocky object about 400 meters long, unlike anything normally found in the Solar System. Loeb discusses his hypothesis and how he came to it, his new book Extraterrestrial, and much more in this week’s episode of Planetary Radio. Pictured: An artist’s impression of ‘Oumuamua. Image credit: ESO/M. Kornmesser.

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Celebrate the 50th anniversary of NASA’s Apollo 14 mission. Planetary Society Chief Advocate and Senior Space Policy Advisor Casey Dreier will be speaking at two free virtual events from the Queens Public Library. At the 1 February event, learn about the historical roots of Apollo, including the agendas and global currents responsible for this unprecedented mission of exploration. Then, at the 4 February event, take a look at Project Artemis—named after the twin sister of Apollo—and the future of lunar exploration. To learn more, check out our new page about the Apollo 14 mission.

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Learn more about the United Arab Emirates’ Hope mission to Mars. On 1 February at 9 AM ET / 2pm UTC, the US-UAE Business Council will host Her Excellency Sarah Al Amiri, UAE Minister of State for Advanced Technology, for a conversation about the UAE-US scientific partnerships that enabled the launch of the Emirates Mars Mission. The conversation will be moderated by Planetary Radio host Mat Kaplan. Register here, and submit your questions in advance by emailing Ameer Alsamman at [email protected].

What's Up

Mars illustration

Mars is looking bright and reddish high in the evening sky. Although Uranus is up, the Moon’s light will make spotting it even more difficult than usual. Learn more at

Wow of the Week

Planetfest 97

Planetfest is a longstanding tradition of The Planetary Society, celebrating major landings and mission milestones over the past 40 years. This vintage poster is from Planetfest '97, a 3-day event celebrating the landing of the Mars Pathfinder mission. Planetfest ’21 will be the first time we’ve ever hosted an all-virtual Planetfest, which means that for the first time people from all around the world can participate.

Do you have a suggestion for the Wow of the Week? We’re looking for space-related art, music, gadgets, quotes, fashion, burning questions, brief sci-fi passages, or anything else that will make our readers go “Wow!” Send us your idea by replying to any Downlink email or writing to [email protected], and please let us know if you’re a Planetary Society member.