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Potential biosignature discovery could boost prospects of Venus missions
by Jeff Foust — September 15, 2020

VERITAS is a proposed Venus orbiter mission that lost in the previous round of NASA's Discovery program but is a finalist again in the ongoing Discovery competition. Credit: NASA/JPL-Caltech

WASHINGTON — The discovery of a molecule in the atmosphere of Venus associated with life could boost the prospects for both government and private missions to the planet.

In a paper published in the journal Nature Astronomy Sept. 14, a group of astronomers reported the discovery of the molecule phosphine in the atmosphere of Venus. The molecule, made of phosphorus and hydrogen atoms, was initially detected with the James Clerk Maxwell Telescope, a telescope that observes in the far infrared and microwave wavelengths in Hawaii, and later confirmed with the Atacama Large Millimeter/submillimeter Array in Chile.

On Earth, phosphine is created by life in anaerobic, or oxygen-free, environments. One possibility for the phosphine found in Venus’s atmosphere is that life in the upper atmosphere may be creating it, but scientists involved with the discovery said there was no definitive proof yet of life there. They added, though, that they had not found an alternative mechanism for creating the phosphine they detected.

“That really left us with two possibilities,” said William Bains of the Massachusetts Institute of Technology, one of the authors of the paper, in a Royal Astronomical Society (RAS) press conference Sept. 14. “The first is that there is some completely unknown, exotic and therefore very exciting chemistry going on in the clouds of Venus that nobody has speculated on before. Or — and this is the more exciting one — the phosphine is being created by life.”

The idea there may be life in the clouds of Venus is not new. While the planet is known for its hot, dense atmosphere that contains sulfuric acid, conditions are more hospitable in the upper atmosphere where temperatures and pressures are lower. Scientists, including the late Carl Sagan, have speculated for decades that life could exist in those upper atmospheric regions, but lacked strong evidence for it.

The phosphine detection could change that. “We are not claiming that we have found life on Venus,” said Sara Seager of MIT, also part of the discovery team. But, she added, “on Earth, phosphine is only associated with life.”

To determine if that phosphine is produced by life, or instead by some other chemical processes, scientists called for more observations, including by spacecraft missions. “We’d like to see really any kind of mission go back to Venus, something that’s capable of measuring gases in the atmosphere,” Seager said. Such missions could also include mass spectrometers to identify more complex molecules linked to life. “We have a long list of things we’d like.”

Venus missions have struggled to win funding in the past. NASA’s last dedicated Venus mission was Magellan, a radar-mapping orbiter launched three decades ago. The most recent missions have been the European Space Agency’s Venus Express, an orbiter launched in 2005, and the Japanese space agency JAXA’s Akatsuki orbiter, launched in 2010.

Two Venus missions were among the five finalists in the previous round of NASA’s Discovery program of lower-cost planetary science missions. However, in early 2017 NASA instead selected two asteroid missions, Lucy and Psyche, and provided additional study funding to a third, the near Earth asteroid telescope mission NEOCam.

In the ongoing competition for Discovery-class missions, two of the four finalists would go to Venus. One, DAVINCI+, would send a probe into the planet’s atmosphere to study its composition. The other, VERITAS, is an orbiter to map the surface using radar. NASA plans to select two missions for development next year.

Other countries are working on, or considering, Venus missions. EnVision is a Venus orbiter mission that is one of three finalists for ESA’s next medium-class mission, launching by the early 2030s, to study the planet’s surface and atmosphere. Russia, a leader in Venus exploration during the Soviet era, is working on a mission concept called Venera-D launching no earlier than 2026 with both an orbiter and a lander. The Indian space agency ISRO is working on a Venus orbiter called Shukrayaan-1 that would launch no earlier than 2023.

At least one privately funded mission is also under study. In recent weeks Peter Beck, chief executive of Rocket Lab, has discussed sending a small spacecraft mission to Venus in 2023. That mission would launch on his company’s Electron rocket and use a version of the Photon satellite bus demonstrated in orbit in a launch last month.

Beck said in a Sept. 3 call with reporters about Photon development that he was motivated to pursue a Venus mission because he thought the planet was overlooked when compared to Mars. “For me, Venus is the more intriguing planet,” he said, both to understand how the planet’s evolution diverged from Earth as well as to look for potential life in the atmosphere.

Doing a Venus mission outside of government agencies, he said, could also shape the future of space exploration more generally. “A private mission to another planet sets a trajectory for where we need to go,” he said. “It’s a real turning point in space if private missions can occur.”

Beck said he was assembling a “pretty amazing” science team, but did not disclose with whom he was working. At the RAS briefing, Seager said she had been in discussions with Beck about a Venus mission. The spacecraft, she said, would weigh only about 15 kilograms, of which 3 kilograms would be available for a science payload. “We have to work hard to make sure an instrument that would be useful for the search for life will fit into that payload,” she said. “We’re really looking forward to it.”

Other private efforts are also emerging. Breakthrough Initiatives, a private foundation funded by billionaire Yuri Milner, announced Sept. 15 it would fund research into potential life on Venus. That effort, according to a statement by the foundation, will include work to “analyze the technical challenges of an exploratory mission in the event that such evidence proves compelling.”

The phosphine discovery could also tip the scales for government missions. The announcement came just as work is starting on a new planetary science decadal survey, with the steering committee for that study announced Sept. 14. That study, which will identify priorities for planetary science missions and related research for the next decade, is scheduled to be completed in early 2022.

While NASA was not involved in the phosphine discovery, the agency’s leader weighed in about it. “The discovery of phosphine, a byproduct of anaerobic biology, is the most significant development yet in building the case for life off Earth,” NASA Administrator Jim Bridenstine tweeted. “It’s time to prioritize Venus.”


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Odp: [SN] Hints of life renew interest in Venus, and a private mission
« Odpowiedź #1 dnia: Wrzesień 16, 2020, 02:38 »
Hints of life renew interest in Venus, and a private mission could lead the way (1)
September 14, 2020 Stephen Clark

A synthesized false color image of Venus, using 283-nm and 365-nm band images taken by the Venus Ultraviolet Imager (UVI) on Japan’s Akatsuki orbiter. Credit: JAXA / ISAS / Akatsuki Project Team

The announcement Monday of the discovery of phosphine gas in the clouds of Venus — an indicator of possible life — has raised hopes among scientists for new robotic missions to renew exploration of Earth’s planetary neighbor.

If Rocket Lab founder Peter Beck gets his way, a privately-funded mission could get the next crack at probing Venus’s soupy atmosphere. NASA Administrator Jim Bridenstine also tweeted Monday: “It’s time to prioritize Venus.”

“Life on Venus? The discovery of phosphine, a byproduct of anaerobic biology, is the most significant development yet in building the case for life off Earth,” Bridenstine wrote.

Venus is home to a hellish landscape that lies at the bottom of an opaque atmosphere made of carbon dioxide, with scorching surface temperatures as hot as 880 degrees Fahrenheit (471 degrees Celsius). Sometimes called Earth’s “evil twin,” it’s the closest world to our own.

At Venus’s scalding surface, the atmosphere is 90 times thicker than Earth’s, similar to the crushing pressure you would find 3,000 feet (900 meters) under the ocean. That doesn’t seem like an environment ripe for life.

But scientists have suggested simple life forms could take refuge high in Venus’s atmosphere, where temperatures and pressures are similar to conditions found at sea level on Earth. Astronomers announced Monday that observations through ground-based telescopes detected phosphine in Venus’s clouds.

Phosphine, made by combining a phosphorus atom with three hydrogen atoms, is only generated on Earth from microbes and industrial activity, scientists said. While a sliver of Venus’s atmosphere has the right temperature and pressure to harbor life, the region strewn with droplets of sulfuric acid and lacks water.

“The real challenge is seeing whether any form of life could evolve to adapt to the incredibly acidic environment,” said Jane Greaves, a professor at Cardiff University in the United Kingdom who led the team that discovered the phosphine signature, in an interview with Astronomy Now. “We just have no analogy (to those conditions) on Earth.”

Scientists have also struggled to come up with how other types of chemical reactions might produce phosphine at Venus, and the ambiguity led Greaves and her team to conclude the discovery could point to “aerial” life forms suspended in the atmosphere.

There’s one spacecraft currently flying around Venus — Japan’s Akatsuki orbiter — but its just the second orbiter sent on a dedicated mission to Venus in 30 years. The European Venus Express mission operated in orbit around the planet from 2006 through 2014.

Both missions have primarily observed the atmosphere of Venus.

The best maps of Venus’s surface were produced by NASA’s Magellan orbiter, which bounced radar beams off the planet to measure its topography — with coarse resolution by today’s standards — from 1990 through 1994. And the last landing on Venus occurred in the 1980s.

That could change in the coming years, with several concepts for robotic missions in the running for funding from NASA, the European Space Agency, Russia, and India.

But none are sure to be approved. NASA has bypassed Venus proposals in past mission competitions, favoring robotic explorers destined for asteroids and other planets.

“It’s like being a (Chicago) Cubs fan,” joked Darby Dyar, chair of NASA’s Venus Exploration Analysis Group. “Venus just never wins.”

This view of the northern hemisphere of Venus was created using more than a decade of radar investigations culminating in the Magellan mission in the 1990s. The image is centered on the planet’s north pole. The Magellan spacecraft imaged more than 98 percent of the planet Venus. This composite image was processed to improve contrast and to emphasize small features, and was color-coded to represent elevation. Gaps in the elevation data from the Magellan radar altimeter were filled with altimetry from the Venera spacecraft and the Pioneer Venus missions. Credit: NASA/JPL/USGS

Meanwhile, NASA has landed spacecraft on Mars eight times, and the space agency launched the $2.7 billion Perseverance rover toward the Red Planet in July on the first leg of a round-trip mission to return Martian soil to Earth for analysis. Perseverance is the latest step in a series of interconnected missions to Mars, each building upon the discoveries and accomplishments of the one before.

The Mars landers have found that the Red Planet was habitable billions of years ago, with running water and other ingredients necessary for microbial life. So far, there’s no sign of extant life on Mars.

Like Mars, Venus has followed an arc of changing climate that stripped away the ocean of liquid water scientists believe once existed there. But instead of getting colder like Mars, Venus was enveloped in a shroud of carbon dioxide that drove a runaway greenhouse effect, pushing temperatures to extremes not found on any other planet in the solar system.

‘We have better topographic data for Pluto than we do for Venus’

“I think it’s time for NASA to start laying the foundation for a program at a different planet,” said Dyar, a planetary geologist and professor of astronomy at Mount Holyoke College.

“The knowledge gap is huge,” she said. “I always start out by saying that we have better topographic data for Pluto than we do for Venus. Imagine if we had a topographic map of Earth, and the resolution was in kilometers instead of centimeters. So we don’t know the topography. We don’t know the rock type.

“We don’t know the actual surface age very well,” Dyar said, highlighting uncertainties about whether Venus harbors active volcanoes. “Venus has a shortage of surface craters, but whether the surface is 150,000 years old or a billion years old, we don’t know.

“So there’s just an enormous amount of information that we are lacking on Venus, and it’s shameful because Venus is the only other planet in our solar system that had liquid water for over a billion years,” she said.

Dyar said Earth’s neighbor toward the sun should be a priority for exploration “because of the lines of evidence — the phosphine discovery being front and center — about the habitability of Venus.”

“I think Venus has got a bit of a tough rap,” said Beck, Rocket Lab’s founder and CEO, in a Sept. 3 press conference.

That’s a sentiment echoed by Dyar on Monday.

“I find it incongruous that we’ve spent so much time on a Mars program when the planet that actually had liquid water for a long time has been relatively unexplored,” Dyar told Spaceflight Now.

“NASA has had an emphasis on following the water and following life,” Dyar said. “Those were the slogans for the Mars program for a long time. At Venus, following water and following life requires multiple kinds of missions.”

Beck said he supports exploring Mars, but he finds Venus more intriguing.

“Venus is Earth gone wrong, and I think there’s a tremendous amount to learn from Venus, especially as we face more and more issues with climate change and trying to understand that,” Beck said. “From a scientific standpoint there’s just an incredible wealth of discovery there.”

Rocket Lab founder and CEO Peter Beck. Credit: Rocket Lab

Speaking before Monday’s announcement on the detection of phosphine, Beck identified the clouds of Venus as a particularly interesting target for research.

“For me, it’s like the ultimate treasure hunt,” Beck said. “Within a sweet zone of the Venusian atmosphere, sort of a 50-kilometer zone, the atmosphere is relatively temperate and — at least in theory — could harbor life. It might not be the life that we’re familiar with today … Really, this is a huge passion. It has been for a long time, and what bigger question is there to answer than how significant or unique life is.”

Putting together a private mission to Venus

The mission Beck is planning would send an entry probe in the atmosphere of Venus. It wouldn’t answer all the questions scientists have about Venus, but could open doors to new ways of exploring the solar system, Beck said.

With its light-class Electron rocket and Photon spacecraft platform, Rocket Lab could deliver nearly 60 pounds — about 27 kilograms — of useful payloads to Venus, according to Beck.

“It might not sound a lot, but 27 kilograms is a lot of radio. That’s a lot of science instrument,” Beck said. “It’s a lot of really good stuff. So we can do some pretty incredible things with that.”

A fully loaded Photon spacecraft weighs a little more than 300 kilograms, or 660 pounds, when it launches on an interplanetary mission, Beck said. Most of that is propellant and on-board systems needed to carry the science payload.

The Photon is about twice the size of a standard American kitchen dishwasher. The mission concept supported by Rocket Lab would release an atmospheric entry vehicle at Venus, while the Photon mothership sails by the planet.

“The mere fact of trying is a great success,” Beck said. “Getting to Venus if a great success. If we can get a probe into the atmosphere, that’s an incredible success. The chances of us finding something that resembles life is incredibly low, but you can’t win the lottery if you don’t buy a ticket.

If Beck’s plans come to fruition, the private mission could be the next spacecraft to reach Venus. In a recent interview with Spaceflight Now, he said Rocket Lab is committed to the mission and plans to launch it by 2023.

“To lay some certainty around it, this is not a brainstorm,” he told Spaceflight Now. “So this is is not, let’s see if we can try and do it. We’re going to Venus. There are no ifs, buts, or maybes.”

Rocket Lab, a U.S. based company, launched its first Photon spacecraft into low Earth orbit Aug. 30 on a demonstration mission. Rocket Lab developed the Photon platform to accommodate a range of space sensors to support Earth-imaging, communications, and scientific missions for military, research and commercial use.

The Photon is based on Rocket Lab’s Curie kick stage, which flies on top of the company’s two-stage Electron small satellite launcher. Fitted with solar arrays, an engine, and other systems for long-duration flight in space, the Photon craft took off on top of an Electron rocket Aug. 30 from Rocket Lab’s launch site in New Zealand.

The rocket deployed a small commercial radar remote sensing satellite for Capella Space, then the Photon spacecraft — which acted as the kick stage on Aug. 30 mission — began its own in-orbit experiments. Rocket Lab announced the milestone Sept. 3, and did not disclose the Photon’s presence on the mission before launch.

Rocket Lab says the Photon will allow the company to be a one-stop shop for space missions, providing the launch vehicle and spacecraft platform to customers in an all-in-one package. Clients will only need to supply an instrument, sensor or payload to mount on the Photon spacecraft, according to Beck.

An upgraded Photon spacecraft with a more capable propulsion system will fly a NASA payload to orbit the moon next year, and the same system could be tailored for more distant destinations with few changes.

There’s no name yet for Rocket Lab’s Venus mission — Beck said he hasn’t thought about that at all — but engineers designed the Photon spacecraft with interplanetary voyages in mind.

“We have the ability to get there,” he said. “We’re building a really fantastic science team, and we have a way to sample the atmosphere.”

Beck emphasized his desire to fund the Venus mission through private sources.

“If I’m going, I’m going to Venus privately,” he said. “I think it’s super important for (it to be) a private mission because just the mere fact of trying to do it raises the bar. A private mission to another planet is something that’s never been done before, or attempted before, and I think that once you show that can be done, that leads the way for a bunch more missions in the future.”

Beck said the private space industry can make “huge advances” in exploration, similar to the way private funding helped pay for the first large astronomical telescopes.

“Typically, these things have always required governments, and I think it’s a real turning point in space if private missions can occur to other planetary bodies,” Beck said.

While he declined to disclose possible teaming arrangements with other companies and scientific institutions, Beck said Rocket Lab is working with “the best of the industry” on the Venus mission.

“We’re trying to pull together a team of some of the best in the field because one of the biggest challenges here is deciding what instrument we’re going to fly,” Beck said. “You have to make some assumptions about what you might find there to be able to design the instrument.”

Sara Seager, an astronomer and planetary scientist on the team that made the phosphine discovery, said Monday she is looking forward to partnering with Rocket Lab on a Venus mission.

“We have been talking to them,” Seager said Monday.

Seager discussed different numbers than those provided by Beck.

“Rocket Lab’s spacecraft would only be about 15 kilograms (33 pounds), and they would reserve about 3 kilograms (6.6 pounds) or so for payload,” Seager said. “So we have to work hard to make sure an instrument that would be useful for the search for life would fit into that payload, and we’re really looking forward to it.”

NASA’s contract with Rocket Lab for the launch and delivery of a compact satellite to lunar orbit next year is valued at $10 million, more than an order of magnitude less than the cost of other U.S. probes sent to the moon. The cost savings are largely driven by the miniaturization of spacecraft technology, such as instrumentation and radios for deep space missions, along with Rocket Lab’s commercial launch service.

Going to Venus may cost somewhat more than $10 million, but Beck said the figure gives a “sense what you can do with such a small amount of money.”

“That’s the thing that excites me the most, really,” Beck said. “For a pretty small amount of money, comparatively speaking, you can go do a mission like that for NASA to the moon, or go further on.”

He said a “number of interests” will fund the Venus mission, including wealthy benefactors, Rocket Lab’s own resources, and Beck himself.

“So between us all, we’ll be able to get there,” Beck said. “What I’d really love to do is not one mission, but three missions. So if anybody wants to join the team, we’d love to hear from them.

“Right now, we can get one mission, but I’d really love to do another couple of missions because that really gives us the ability to learn much more and have meaningful cracks at it.”

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Odp: [SFN] Hints of life renew interest in Venus, and a private mission
« Odpowiedź #2 dnia: Wrzesień 16, 2020, 02:40 »
Hints of life renew interest in Venus, and a private mission could lead the way (2)

Artist’s illustration of Rocket Lab’s Photon satellite bus. Credit: Rocket Lab

Rocket Lab have the mission ready for launch in early 2023. “The spacecraft design is largely complete with the lunar mission,” Beck said. “We’ll be moving pretty quickly into starting to build some hardware.”

A private mission run by Rocket Lab would be an appetizer for scientists with a hunger for fresh data on Venus.

Scientists see opportunity for Venus to grab spotlight in planetary science

Just like at Mars, scientists need a fleet of orbiters and landers to build up a better understanding of Venus and its history, Dyar said.

“And then it requires things in between that can understand the structure of the atmosphere,” she continued. “We don’t know much about the lower atmosphere below about 30 kilometers (18 miles).”

“We’d like to see really any kind of mission go back to Venus, something that’s capable of measuring gases in the atmosphere,” Seager said. “Something that has a so-called mass spectrometer that can identify larger complex molecules that can only be associated with life.”

“We’re really hoping somebody, maybe in the private space industry … might take this up,” Greaves said Monday.

Addressing the most daunting questions about Venus will require a substantial financial commitment, likely in the form a multibillion-dollar “flagship” mission, Dyar said. NASA typically builds and launches one or two robotic interplanetary flagship missions per decade.

NASA will try to launch three flagship solar system missions in the 2020s. One was the Perseverance Mars rover, and the next will be a sophisticated spacecraft to orbit Jupiter and perform repeated flybys of the icy moon Europa. The third could be a joint mission by NASA and the European Space Agency to retrieve the Martian samples gathered by the Perseverance rover for return to Earth.

That means the following flagship mission probably won’t launch until the 2030s.

An independent panel of scientists will release a report in 2022 with priorities for the next decade of solar system exploration, beyond the Europa Clipper and Mars Sample Return missions. Within budgetary limitations, NASA’s policy is to follow the science community’s recommendations.

A flagship mission to Venus might include an orbiter, a long-life lander, and a balloon that could float among the Venusian clouds. Such a project might be able to tackle many objectives at once, such as studying Venus’s geology and directly sampling Venus’s atmosphere.

“A balloon is certainly the best way,” Seager said.

The Soviet Union’s Vega missions floated balloons in the atmosphere of Venus. Similar balloons today could carry a much more moden set of instruments.

“That’s the kind of thing we’d like to see happen again,” Seager said. “Perhaps a super version of those (Vega balloons) that instead of lasting a couple of days, could last a week, months, even a couple of years.”

A Venus flagship will be in stiff competition to receive the top ranking from the decadal survey.

The decadal survey scientists will weigh a Venus mission against flagship concepts to land on Mercury, drive more than 1,000 miles across the moon, deploy a network of geophysics stations on the lunar surface, or dispatch multiple orbiters to Mars to map underground ice and collect global climate data.

Other decadal survey flagship candidates with detailed concept studies commissioned by NASA include a mission that would return samples to Earth from the icy dwarf planet Ceres, a spacecraft to orbit and land on the frozen shell of Saturn’s moon Enceladus, an orbiter and atmospheric probe to Neptune and its moon Triton, and a mission to orbit Pluto.

If Venus doesn’t come out near the top of the decadal survey’s ranking, the world’s space agencies are considering smaller-scale Venus missions in ongoing competitions for funding.

NASA last year selected four proposals from scientists for the next mission in the agency’s Discovery program, a line of cost-capped robotic interplanetary probes. Two of the missions would go to Venus, and two other concepts would travel to Neptune’s moon Triton and Jupiter’s volcanic moon Io.

After reviewing the mission proposals on their scientific merit, technical readiness and cost, NASA plans to select one or two next April for full development ahead of launch opportunities in 2026.

The proposed Venus missions under consideration by NASA are named VERITAS and DAVINCI+. Those names are short for Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy, and Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging Plus.

Artist’s concept of an entry probe like the one being designed for NASA’s proposed DAVINCI+ mission. Credit: NASA

NASA has not launched a mission to Venus since 1989, when the Magellan radar mapper set off from Earth to peer beneath Venus’s thick clouds and map the planet’s volcanic landscape.

The last U.S.-led mission to send a probe into the atmosphere of Venus was Pioneer Venus in 1978. The Soviet Union’s Vega missions were the last to plunge deep into Venus’s atmosphere in 1985.

The DAVINCI+ mission would send a descent probe into the atmosphere of Venus to precisely measure its composition down to the surface, according to NASA. The mission would help scientists understand how the atmosphere formed and evolved, and accumulate more information about the history of water at Venus.

A hardened “sphere” will carry the instruments to the surface of Venus, measuring atmospheric composition and conditions at various altitudes throughout a gradual hour-long descent. Cameras on the descent sphere and an orbiter component to the mission will map surface rock types, according to NASA.

The VERITAS mission would carry a synthetic aperture radar instrument on an orbiting spacecraft to survey nearly the entire surface of the Venus, according to NASA. The VERITAS orbiter would collect data on the types of rock that make up Venus’s crust, and like DAVINCI+, would pursue signs of ancient water on the planet.

If selected by NASA, the DAVINCI+ and VERITAS missions would have to each fit under a $500 million cost cap, excluding launch expenses and international contributions.

The European Space Agency is also weighing a selection of its next medium-class, cost-capped science mission. One of the European finalists, named EnVision, is a proposed orbiter that would launch to Venus in 2032 with similar objectives as VERITAS — to map the planet in unprecedented detail with radar.

EnVision would come with a cost limit to ESA of 550 million euros, or around $650 million. Science instruments provided by other space agencies do not count against the cost cap.

Russia’s Venera-D mission is in the early stages of development. Venera-D would consist of an orbiter and a lander, with a launch no earlier than the late 2020s. The Russian mission would build on the Soviet Union’s Venera probes, which made the first soft landings on Venus.

India’s space agency also also proposed a Venus orbiter that could launch as soon as 2023 with instruments focusing on studying the planet’s hazy atmosphere. Like the NASA and European concepts, the Indian mission is awaiting final approval before proceeding into development.


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Odp: [PAP] Dr Pętkowski: pojawia się nowa tajemnica
« Odpowiedź #3 dnia: Wrzesień 17, 2020, 01:37 »
Dr Pętkowski: pojawia się nowa tajemnica związana z tym, czy istnieje życie na Wenus
15.09.2020  Ludwika Tomala

fot: Janusz Pętkowski, materiały prasowe

Naukowcy odkryli w chmurach Wenus fosforowodór. "Albo nie rozumiemy chemii planet skalistych, albo mamy pierwszą potencjalną sugestię, że w chmurach Wenus istnieje życie" - mówi PAP współautor badań dr Janusz Pętkowski z MIT. I dodaje, że to kolejna tajemnica związana z tym, czy na Wenus życie jest możliwe.

PAP: Co państwo właśnie ogłaszają światu?

Dr Janusz Pętkowski, astrobiolog z grupy badawczej prof. Sary Seager w Massachusetts Institute of Technology: Zespół naukowców pod przewodnictwem Jane Greaves z Uniwersytetu w Cardiff - w tym również ja - odkryliśmy obecność fosforowodoru, zwanego też fosfiną, w atmosferze planety Wenus. A dokładniej w chmurach, na wysokości ok 55 km nad powierzchnią tej planety. Badania ukazały się w Nature Astronomy.

PAP: Co to jest fosforowodór?

JP: To gaz, w którego skład wchodzi atom fosforu i trzy atomy wodoru (PH3). Odkrycie tego związku w chmurach Wenus jest o tyle nieoczekiwane, że na chwilę obecną nie znamy procesów, które by wytwarzały ten gaz - np. w procesach geologicznych albo w atmosferze - na planetach skalistych takich jak Wenus czy Ziemia. Wiadomo za to, że na Ziemi fosforowodór jest produkowany wyłącznie przez życie lub jest wytwarzany w procesach przemysłowych.

PAP: Gdzie na Ziemi powstaje fosforowodór?

JP: Wytwarzają go beztlenowe organizmy, które żyją w środowisku całkowicie pozbawionym tlenu: na bagnach, mokradłach, czy nawet we wnętrzu naszego układu pokarmowego. Fosforowodór jest również produktem procesów przemysłowych.

PAP: Co więc oznacza odkrycie fosforowodoru na Wenus?

JP: Są dwie możliwości. Albo na Wenus dochodzi do produkcji fosforowodoru w wyniku kompletnie nieznanych nam procesów fizycznych, chemicznych, geologicznych czy fotochemicznych. Albo mamy do czynienia z tym, że ewentualnie w chmurach Wenus istnieje jakieś życie. Oba te warianty są nieprawdopodobne! Albo nie rozumiemy chemii planet skalistych, albo mamy pierwszą potencjalną sugestię, że na tej sąsiadującej z Ziemią planecie możliwe jest życie.

PAP: Czy to znaczy, że odkryli państwo życie w chmurach Wenus?

JP: Nie, to nie jest ostateczny dowód na istnienie życia. Ale to sugestia, że w atmosferze naszej sąsiedniej planety istnieją procesy, których nie rozumiemy. Jedną z możliwych hipotez na wyjaśnienie tych procesów jest życie.

PAP: Co właściwie zakłada hipoteza, którą państwo prezentujecie? Że w chmurach Wenus unoszą się jakieś mikoorganizmy?

JP: Jeśli nawet założymy, że fosforowodór ma związek z obecnością życia, to na razie i tak nie moglibyśmy powiedzieć, jak to życie wygląda i czym ono jest. Wykryliśmy tylko ewentualny produkt metabolizmu organizmów żywych. Jeśli okaże się, że to życie, to ono musi funkcjonować w wyłącznie w atmosferze, w chmurach, pewnie bez kontaktu z powierzchnią planety, która jest za gorąca. Temperatura powierzchni planety to ok. 465 stopni Celsjusza. Ale jak miałoby funkcjonować takie życie i czy to są mikroorganizmy - nie wiadomo. Jedyną możliwością, żeby to sprawdzić, jest polecieć na Wenus i zbadać próbki z chmur.

PAP: Niech pan opowie o tych wenusjańskich chmurach!

JP: Na Ziemi chmury składają się z wody. A skład chmur na Wenus to w 85 proc. kwas siarkowy i w 15 proc. woda.

PAP: Stężony kwas siarkowy? Oj!

JP: Tak, dla nas, Ziemian, to nie do pomyślenia. Nawet najbardziej ekstremofilne bakterie żyjące na Ziemi by sobie w takim środowisku nie poradziły. Kwas siarkowy to jednak rozpuszczalnik, ciecz. A obecność jakiejś cieczy jest niezbędna do tego, by życie mogło funkcjonować. Nie wiemy, czy jakieś życie jest w stanie funkcjonować w tak dużym stężeniu kwasu siarkowego.

PAP: Jeśli życie istnieje na Wenus, to biedne jest to życie…

JP: Jeżeli okaże się, że w chmurach Wenus jest życie, to musiałoby być życie kompletnie inne niż to, które znamy. W teorii jednak można by było zbudować biochemię kompatybilną z kwasem siarkowym. Można przecież sobie wyobrazić, że dla innych form życia nie do pomyślenia jest życie na Ziemi - przy tak dużej obecności tlenu, który wszystko utlenia. My się jednak dostosowaliśmy. Tlen nie jest naszym wrogiem, jakim był jeszcze 3 mld lat temu. A stał się dla nas koniecznością. Czy analogiczna sytuacja mogła mieć miejsce na Wenus, gdzie kwas siarkowy stał się niezbędny do życia? Nie wiadomo. Ale możemy się nad tym zastanawiać.

PAP: Ale skąd by się - hipotetycznie - miało wziąć życie w chmurach Wenus?

JP: Są modelowania klimatu Wenus, które sugerują, że Wenus przez miliardy lat wyglądała jak Ziemia. Miała np. oceany ciekłej wody, rzeki, jeziora. Ok 700 mln lat temu doszło tam jednak do kataklizmu, który sprawił że Wenus zmieniła się w “piekielną planetę”, jaką teraz znamy. Jest pytanie, czy jakieś życie mogło przetrwać ten kataklizm. A akurat w chmurach - przynajmniej pod względem temperatury - życie mogłoby sobie poradzić. W chmurach Wenus - na wysokości 55 km - temperatury wynoszą między 20 a 60 stopni C, a więc o wiele łatwiej tam byłoby przetrwać.

PAP: Może zatem fosforowodór to ślady po życiu, które istniało na Wenus miliony lat temu?

JP: Nie, fosforowodór jest reaktywnym gazem, jest niszczony fotochemiczne w atmosferze. Fakt, że on tam istnieje, oznacza, że teraz musi zachodzić tam proces, który ciągle go produkuje. Fosforowodór musi być więc stale uzupełniany w atmosferze planety.

PAP: Czy fosforowodór jest równomiernie rozłożony w atmosferze? Czy może znaleziono go w jakimś konkretnym obszarze Wenus?

JP: Obecność fosforowodoru potwierdziły obserwacje dwóch teleskopów: teleskopu JCMT na Hawajach i teleskopu ALMA w Chile. JCMT był w stanie określić, na jakiej wysokości w chmurach występował gaz, a ALMA dodatkowo określiła, że fosfina jest obecna w pasie geograficznie analogicznym do naszych szerokości geograficznych klimatu umiarkowanego. Gaz więc nie powstaje na biegunach Wenus. Nie znamy powodów takiego rozłożenia fosfiny w atmosferze Wenus. Można więc sobie wyobrazić, że jeśli w tamtejszych chmurach jest życie, to preferuje ono z jakiegoś powodu funkcjonowanie w umiarkowanych szerokościach geograficznych.

PAP: Fosforowodór ma prosty wzór chemiczny PH3… To nie brzmi jak skomplikowany w produkcji związek chemiczny.

JP: Tylko na pierwszy rzut oka. Ten gaz był już wcześniej odkryty na Jowiszu i Saturnie. To jednak olbrzymie gazowe planety. I są tam trzy warunki, które ułatwiają powstawanie fosfiny: wysokie ciśnienie, wysoka temperatura i bardzo duże ilości wodoru. A to warunki, które nie występują jednocześnie na planetach takich jak Wenus i Ziemia. Nie mamy pojęcia jak fosforowodór mógłby na takich planetach skalistych powstać. Na Ziemi jest on produkowany przez życie. Czy jest tak też na Wenus? Nie wiemy.

PAP: Specjalnie szukali państwo fosforowodoru, czy przypadkiem go państwo znaleźli?

JP: My na MIT zajmowaliśmy się fosforowodorem od kilku lat. Badaliśmy jego właściwości i zastanawialiśmy się, jak go wykrywać na planetach daleko od nas. Nawet nie przypuszczaliśmy, że gaz ten może być tak blisko nas - na sąsiedniej planecie. A z kolei Jane Greaves szukała w obiektach Układu Słonecznego gazów, które nie pasowałyby do tamtejszej chemii i mogłyby być sygnałem życia. Jednym z nich był właśnie fosforowodór. Jane Greaves wycelowała teleskop w Wenus i okazało się, fosfina tam jest. Nasze grupy połączyły siły i dzięki temu mogliśmy przedstawić hipotezy dotyczące obecności fosforowodoru.

PAP: Czy już wcześniej pojawiały się przypuszczenia, że na Wenus może być życie?

JP: Odkrycie fosfiny dodaje kolejną tajemnicę do listy tajemnic tej planety. Pierwsza tajemnica jest taka, że być może planeta ta przez miliardy lat wyglądała kiedyś jak Ziemia. Drugą tajemnicą jest to, co wiadomo od lat - że w chmurach Wenus jest związek chemiczny, który pochłania 50 proc. promieniowania UV, które pada na planetę. Nikt nie wie, co to za związek blokuje światło. Ludzie zaczęli nawet spekulować, że to może jakiś pigment potrzebny do prowadzenia fotosyntezy w chmurach. Tego ciągle nie wiadomo. A teraz do listy tajemnic Wenus dochodzi jeszcze tajemnica pochodzenia fosforowodoru (to nie on pochłania promieniowanie UV). To lista tajemnic, które sugerują, że Wenus może być ciągle siedliskiem życia.

PAP: No to chyba warto będzie wysłać sondę, która zbada możliwość życia w superkwaśnych chmurach Wenus.

JP: To konieczne. Bez tego nie będziemy w stanie potwierdzić, skąd fosforowodór bierze się w atmosferze Wenus. Czy to geologia, czy to może życie. Jeśli jednak chcemy badać Wenus, ważna jest ochrona planetarna. Nie chcemy przy okazji badań zawlec na Wenus życia z Ziemi. Ani przypadkiem przewieźć na Ziemię życia z Wenus. (PAP)

Rozmawiała: Ludwika Tomala


Polskie Forum Astronautyczne

Odp: [PAP] Dr Pętkowski: pojawia się nowa tajemnica
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