Plate Nº 13 · recorded November 1, 2026
Space & AstronomyReported finding
NASA's Viking 2 Likely Caught Real Marsquakes in 1976, Study Finds
A new AGU Advances study ties Viking 2's 1976 sol 80 signal to the same northern-plains region where InSight later detected nearly 1,000 marsquakes, suggesting a long-lived active zone on Mars.
By Nathan Brooks3 min read677 words
In brief
- Viking 2 recorded two candidate marsquakes on sols 53 and 80 of 1976 in Utopia Planitia.
- NASA's InSight lander detected nearly 1,000 marsquakes between 2018 and 2022.
- The peer-reviewed study, led by Wanbo Xiao of Peking University, appeared in AGU Advances on September 30, 2026.
- The sol 80 event possibly shares a source region with InSight seasonal marsquakes, though a meteorite impact can't be excluded.
- Valles Marineris stretches over 2,500 miles — nine times the length of Earth's Grand Canyon — and is still quake-active.
NASA's Viking 2 lander recorded two candidate marsquakes on September-era sols 53 and 80 of 1976 — and a new peer-reviewed analysis finds one of them likely came from the same region where, four decades later, InSight detected nearly 1,000 more.
The study, led by Wanbo Xiao of Peking University in China, was published in AGU Advances on September 30, 2026. Matthew R. Francis covered the findings for Eos on October 21, 2026. Marsquakes are the Martian equivalent of earthquakes, and they show the Red Planet is still seismically active.
What did Viking 2 actually record?
Viking 2 — the fourth spacecraft from Earth ever to land on Mars — touched down on September 3, 1976, in a northern-lowlands region called Utopia Planitia. Its main job was the search for Martian life, which it didn't conclusively find.
It also carried a seismometer, an instrument that measures ground shaking, mounted on the lander's top deck. That placement made it vulnerable to Martian wind, and scientists struggled for decades to separate real seismic signals from wind vibration. Of the two 1976 detections, on sol 53 and sol 80 (a sol is a Martian day, slightly longer than an Earth day), the first was probably wind noise. The second looked more like a genuine marsquake.
The paper's authors put it plainly:
"For nearly 50 years, scientists debated whether the candidate seismic signals recorded by Viking 2 reflected true Martian tectonics, considering limitations of the Viking instrument."
How does InSight's data change the picture?
InSight landed in November 2018 in Elysium Planitia, geographically adjacent to Utopia Planitia — so similar that scientists often speak of the Elysium-Utopia basin. Unlike Viking 2's deck-mounted sensor, InSight's more advanced seismometer sat directly on the ground, and the mission was purpose-built for seismology. From 2018 to 2022 it logged nearly 1,000 marsquakes.
Xiao's team rebuilt Viking 2's original seismic workflow and reexamined the candidate events using InSight-era knowledge. The sol 80 signal, they found, possibly originated in the same northern-plains source region as InSight's seasonal marsquakes — hinting at a long-lived active zone outside the known Cerberus Fossae hotspot.
The confirmation isn't airtight, though. The researchers write that "a distant tectonic marsquake or a meteorite impact remain as alternative explanations."
Why do the two data sets look so different?
The apparent mismatch between Viking 2's sparse detections and InSight's bounty has a mundane explanation: the hardware. The team concluded:
"Our analysis reveals that the apparent contrast between Viking and InSight seismic observations primarily reflects differences in instrument response, sampling strategy, and the distinct spectral characteristics of Martian seismic events, rather than a change in Martian activity alone."
One physical clue stands out. The sol 80 event decayed faster than typical InSight marsquakes, which could point to lateral variations in how the Martian subsurface absorbs seismic energy.
The study's broader lesson, as the authors note, is that a historical planetary data set can gain fresh scientific meaning when revisited with later mission data.
Where else is Mars shaking?
InSight's seismic record has fingered several active regions:
- Valles Marineris: Researchers at Columbia University and Imperial College London reported this month that Mars' "Grand Canyon" — over 2,500 miles (4,000 km) long, nine times the length of Earth's Grand Canyon — is still experiencing marsquakes.
- Cerberus Fossae: Mars' primary seismic hotspot, east of InSight's landing site, where hundreds of quakes traced back to magma movement, localized faulting, and active stress release.
- Tharsis volcanic region: Home to Olympus Mons and the three Tharsis Montes volcanoes; distant, low-frequency quakes suggest deep mantle activity or residual cooling.
- Impact quakes: Several non-tectonic signals came from meteoroid strikes, confirmed when Mars orbiters spotted fresh craters in regions like Amazonis Planitia and Cerberus Fossae.
The bottom line: two faint signals from 1976 now fit a pattern of nearly 1,000 quakes — strong evidence that Mars never stopped shaking, only that our instruments finally got good enough to prove it.
via agupubs.onlinelibrary.wiley.com (Original)
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