金星に送られた探査機の残骸、まだ残っている可能性

Scientists long assumed Venus’s harsh environment would quickly destroy artifacts from probe missions. But a new study makes a compelling case to the contraryBy Emma Gometz edited by Lee BillingsAn artist's impression of NASA's DAVINCI probe descending toward the surface of Venus. NASAWhen international space agencies send probes out into the solar system, many are abandoned to expire and deteriorate on extraterrestrial terrain. But if they’re still out there, can we learn something from them?Space archaeologists have mostly ignored things sent to our sister world, Venus. Sometimes called “Earth’s evil twin,” Venus is nearly identical to our own planet in simple terms of mass and bulk composition, albeit with quirks that make it extremely inhospitable to humans and machines alike. Many researchers had assumed that all robotic missions sent there would so thoroughly succumb to Venus’s brutal combo of scorchingly hot surface temperature and crushingly high atmospheric pressure that little would be left behind for subsequent study. And erupting volcanoes and landslides from “Venusquakes” could bury whatever remained in geologically short order.Last month, however, space archaeologists published a paper that suggests that the Venusian environment may preserve probes far better than once thought.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.Out of 20 probes, landers and balloons sent by the U.S. and Soviet Union that have reached the surface of Venus in the past 60 years, the study found that at least seven were probably hardy enough to endure the hostile environment and ended up in places on the planet where they’re not imminently threatened with geological burial or destruction. “This does not mean that the others cannot be preserved,” says space archaeologist and independent researcher Luca Forassiepi, one of the study co-authors. “But I’d say for those seven ... I don’t find any reason to not think that they are still there.”Reaching that conclusion required somehow replicating the harsh realities of Venus right here on Earth. The planet’s surface is broiling at about 460 degrees Celsius (860 degrees Fahrenheit), about double the temperature required to melt pure tin. The surface also lies beneath 90 bars of pressure, almost 100 times greater than that of sea level on Earth, from a smothering sky filled with near-pure carbon dioxide and laced with corrosive sulfuric acid rain.The study authors used data from NASA’s Glenn Extreme Environments Rig (GEER) lab, which recreated the Venusian environment, to do a case study on how the American Pioneer Venus Day Probe may have fared after it plunged through Venus’s clouds in 1978. The probe was made of mostly titanium, with beryllium shelves and aluminum equipment boxes inside. GEER tests have shown that titanium has “excellent resistance” to Venus’s surface conditions, so the probe should’ve mostly retained its shape, the authors wrote. The probe’s aluminum parts showed similar resilience.The GEER data suggested, however, that the probe’s O-rings and gaskets responsible for maintaining its internal pressurization would have likely failed from prolonged exposure to Venus’s environment. Weakened by a brief-but-corrosive bath of sulfuric acid droplets during its plunge, the probe would’ve inevitably deformed and ruptured upon reaching the ground. But that doesn’t mean it would have been completely destroyed—far from it.“You have to have some kind of deformation, for sure, and compression in the moment of the entrance of the Venus atmosphere and very oxidized, very corroded looking metal,” Forassiepi says. “I’m very hopeful that [if we ever] have a probe with an imaging capability to image an artifact on the surface, we will see it in the same place where we left it.”The Pioneer Venus Day Probe is just one of 20 objects studied, most of which were not American-made. But because of the comparative lack of accessible Soviet-era records, Forassiepi and his co-authors chose the probe as a case study.Their investigation also evaluated what we currently know about Venus’s surface conditions in the areas where all of the probes landed. It factored in estimates of volcanic and seismic activity, radiation levels, meteorite impact rates, and even the manner and speed with which sediments accumulate on the ground. Most of the probes, the researchers found, should still be visible, even if they’re not wholly intact on the surface—and the odds for long-term survival seem favorable because Venus’s geological activity is much more sluggish than that of Earth’s, with far lower levels of volcanism and tremors.The question of how Venus’s atmosphere affects probes isn’t just about the past—the list of artifacts may be growing soon because more probes are set to land on Venus. NASA’s Deep Atmosphere Venus Investigation of Noble Gases, Chemistry and Imaging (DAVINCI) mission, tentatively scheduled for 2030, aims to release a probe meant to land on the planet’s surface and capture images and data. Also, the Massachusetts Institute of Technology and the company Rocket Lab are eyeing a 2026 launch date for their private mission’s Venus-bound probe.The paper “extends the range of space archaeology," says Beth O’Leary, a space archaeologist and professor emerita at New Mexico State University, who was not involved with the study but is mentioned in the paper’s acknowledgments. “Forassiepi has broadened that to a place where we [once] said, ‘Forget it. There’s not going to be anything there.’”Space archaeology provides insight into technological innovation of the past and can help us chart future space missions and engineering projects. But it also preserves human history and what scientists call “space heritage.”“Venus is part of this general effort to study all our material traces in the solar system,” Forassiepi says. “The fact that it’s very difficult to access doesn’t downsize the cultural and historical value.”It’s Time to Stand Up for ScienceIf you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. 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