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Life on Venus: NASA, others weigh missions after phosphine discovery



The next obvious step is to send a robotic probe to take a closer look at something NASA and its Russian counterpart seem interested in doing. The US space agency was already considering moving forward with two different Venus missions, one or both of which could potentially be modified to search for phosphine or attempt a more direct detection of alien organisms.

Russia, meanwhile, has a long history of sending robotic vessels there, and last week the head of Roscosmos, the country’s space agency, called Venus a “Russian planet.”

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But both agencies could also be removed. The day after the news broke, a privately funded organization backed by Russian billionaire investor Yuri Milner, called the Breakthrough Initiatives, announced that it had hired a team of top scientists to investigate ways to get a short-term investigation mission from Venus .

“We just want to do something small, fast and focused,” said Sara Seager, an astrophysicist at MIT who leads the breakthrough study and is also co-author of the paper in Nature Astronomy, which announced the detection of phosphine.

“Can we send a microscope and look for life directly?” she asked. It is conceivable, she said. “Of course we want to see small microbes swimming around.”

Like other scientists, Seager knows that any claim to the discovery of extraterrestrial life would require enormously compelling evidence. Finding phosphine is not the same as finding hard evidence for life.

On Earth, the molecule can be produced through the metabolic processes of life as we know it and through industrial production. The scientists who reported the phosphine discovery on Venus said they could not think of any natural explanation, other than the presence of life, for the abundance of the molecule. And they discovered it in that part of the Venusian atmosphere that is believed to be most comfortable for life.

“All we can say is that we have a reliable detection of phosphine gas in 20 parts per. Billion, coming from 50 to 60 kilometers from the surface, where the temperatures are not too hot, not too cold, but just for life, ”said Seager.

What kind of life? No one knows. The Venuses may have a truly alien biochemistry adapted to one of the harshest environments in the solar system.

Venus is so hot – about 900 degrees Fahrenheit – that the rocks literally glow on the surface. But this was not always the case.

Venus, Earth, and Mars all formed more than 4 billion years ago, and for much of their early history, they had many similarities, including moderate temperatures that allowed water to float on the surface. It is conceivable that life existed on all three planets billions of years ago.

But Venus’ location so close to the sun turned out to be catastrophic. As the young sun got older, it got warmer. The Venus gardens eventually boiled away. It flooded the atmosphere with carbon dioxide, which had previously been largely dissolved in the ocean. The result was a runaway greenhouse effect.

Astrobiologist David Grinspoon from the Planetary Science Institute in Tucson notes that the reflectivity of Venus’ thick cloud cover is what makes the planet so bright in our night sky. The clouds are the result of ongoing volcanic activity, he said.

“So with the naked eye, you can confirm the presence of volcanic activity on our twin planet,” Grinspoon said in an email. “It is hot enough on the surface to melt lead and zinc and some aluminum alloys. The Soviets sent a metallic bust of Lenin into one of their early landers, which should have quickly become a puddle. ”

But higher in the atmosphere, the temperature is more benign. In 1967, astronomer Carl Sagan speculated that microbes could survive in the Venusian clouds. However, because the clouds shoot through with sulfuric acid, these microbes are likely to need a protective shell.

The Soviet Union had a special fascination with Venus and sent groundbreaking space probes there as part of its Venera program starting in the 1960s. The Soviets eventually managed to land six spacecraft on Venus, and they sent back images of a strong, rocky landscape.

“By the late ’60s, Venus’ romance was gone,” said Sanjay Limaye, a University of Wisconsin at Madison Planet Scientist who, like Grinspoon, is a longtime proponent of the Venusian life hypothesis.

Another Venus spokesman is Darby Dyar, a planetary scientist at Mount Holyoke College and chairman of Venus’ NASA advisory committee. She knows that her favorite planet is overshadowed by Mars and estimates the number of Venus specialists as no more than one-tenth of them for Mars. There has not been a major mission to explore Venus in a quarter of a century, she said.

But Venus, she argues, is unfairly overlooked, and planetary science budgets should be more balanced, in part because new research suggests that Venus probably had a comfortable environment for billions of years.

In fact, she said Venus probably had garden before Earth had it. It had plenty of time for life to evolve – potentially into complex organisms. It is not excluded that the rocks in Venus have fossils, she said.

“The probability that there has ever been life on Venus has risen in the air,” Dyar said, referring to research into the life of the Venusian oceans. “There are atmospheric models that show that Venus had as much water as Earth and actually had it before.”

Dyar is one of the scientists pushing on a mission called Veritas, which will send a probe to Venus to map its surface. It is one of four proposed planetary missions competing for NASA funding as part of the agency’s Discovery program, which backs relatively inexpensive robotic explorations of the solar system.

“Right now we know the topography of Pluto” – the dwarf planet at the edge of the solar system – “better than we know the topography of Venus,” she said.

Another proposed mission, DaVinci +, which is under development at NASA’s Goddard Space Flight Center in Greenbelt, Md., Would send a probe through the atmosphere of Venus and to the surface with the goal of understanding the history of water on the planet. According to NASA, the mission’s instruments would be “encapsulated in a specially built descent sphere to protect them from Venus’ intense environment.” The mission would send images of the surface back.

The other two planetary missions competing for dollars are Trident, which would send a probe to study Neptune’s large, icy moon Triton – which may have an underground ocean – and Io Volcano Observer or IVO, which would study one of the four large moons. of Jupiter.

NASA is expected to make its choice next April. The Agency’s response to the phosphine message was particularly cautious. Its administrator, Jim Bridenstine, posted to his blog a description of the many astrobiological programs supported by NASA, but did not promise any special treatment for Venus.

A separate statement from the agency was also ambiguous, but it cited one of the attractive features of Venus as an exploratory goal: It is “a planetary destination we can reach with smaller missions.”

Proximity is, in other words, a cosmological virtue.


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