Planet Venus From Space
An international team of astronomers has detected a rare chemical in the atmosphere of Venus that could be produced by living organisms, according to a study published Monday. The discovery instantly puts the brightest object in the night sky back into the conversation about where to search for extraterrestrial life. The researchers made clear that this is not a direct detection of life on Venus. But the astronomical observations confirmed the presence of the chemical phosphine in the atmosphere. The chemical, produced on Earth by bacteria, is considered a potential “biosignature” of life. There may be bizarre microbes living in the sulfuric acid-laden clouds of the hothouse planet, scientists said.
The scientists said they could find no possible non-biological explanation for the abundance of the chemical in the Venusian atmosphere. Although Venus is broiling at the surface, there are regions in its thick atmosphere that scientists consider to be potentially habitable. For decades, some planetary scientists have suggested that microbes could be circulating in the atmosphere. “We did our very best to show what else would be causing phosphine in the abundance we found on Venus. And we found nothing. We found nothing close,” said Clara Sousa-Silva, research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences.
Computer-Generated View of Surface of the Planet Venus Dominated by the Volcano Sapas Mons
“Any organisms on Venus will probably be very different to their Earth cousins, but they too could be the source of phosphine in the atmosphere,” the researchers said in a news release. Venus has long been overshadowed by Mars as a potential abode of life, because the planet’s dense atmosphere has led to a runaway greenhouse effect, resulting in hellish surface temperatures and crushing atmospheric pressures. Robotic probes have revealed a landscape that appears inhospitable to any imaginable life form. Relatively speaking, Mars is more congenial and has been targeted by many robotic missions, including most recently NASA’s Mars 2020 rover, Perseverance. NASA is pondering proposals for two relatively low-cost robotic missions to Venus, but they have not been approved.
Phosphine is a Noxious Gas that on Earth is Only Associated with Life
Life is definitely a possibility, but more proof is needed, several outside scientists said. Cornell University astronomer Lisa Kaltenegger said the idea of this being the signature of biology at work is exciting, but she said we don’t know enough about Venus to say life is the only explanation for the phosphine. “I’m not skeptical, I’m hesitant,” said Justin Filiberto, a planetary geochemist at the Lunar and Planetary Institute in Houston who specializes in Venus and Mars and isn’t part of the study team. Filiberto said the levels of phosphine found might be explained away by volcanoes. He said recent studies that were not taken into account in this latest research suggest that Venus may have far more active volcanoes than originally thought. But Clements said that explanation would make sense only if Venus were at least 200 times as volcanically active as Earth.
Venus Volcanic Valley
David Grinspoon, a Washington-based astrobiologist at the Planetary Science Institute who wrote a 1997 book suggesting Venus could harbor life, said the finding “almost seems too good to be true.” “I’m excited, but I’m also cautious,” Grinspoon said. “We found an encouraging sign that demands we follow up.” NASA hasn’t sent anything to Venus since 1989, though Russia, Europe and Japan have dispatched probes. The U.S. space agency is considering two possible Venus missions. One of them, called DAVINCI+, would go into the Venutian atmosphere as early as 2026. Clements said his head tells him “it’s probably a 10% chance that it’s life,” but his heart “obviously wants it to be much bigger because it would be so exciting.”
The announcement of the discovery of phosphine could push NASA and other space agencies to take a closer look at Venus. “For something this big, we need follow-up confirmations, we need to have strong scientific debate,' said Casey Dreier, senior space policy adviser at the Planetary Society, a nonprofit pro-space organization. “Ultimately we’re going to need missions to Venus, and maybe even bringing samples back to Earth.”