Venus possibly habitable for billions of years
14:49 08 September 03
NewScientist.com news service
The hellish climate of Venus may have arisen far more recently than previously supposed, suggests new research. If so, pleasant Earth-like conditions probably persisted for two billion years after the planet's birth - plenty of time for life to have developed.
Venus is virtually the same size as Earth and, on average, is our nearest neighbour. Today, its atmospheric temperatures are hot enough to melt lead and concentrated sulfuric acid continuously drizzles down from thick sulphurous clouds that completely block out the Sun.
But the planet once had a climate similar to Earth's and vast oceans of water. Planetary scientists agree that period ended when Venus lost its water due to a runaway greenhouse effect, but the question is when.
Until now, the best estimate, calculated 15 years ago by Jeffrey Kargel, of the US Geological Survey, was four billion years ago - just 600 million years after the Solar System's birth.
But new work by David Grinspoon, at the Southwest Research Institute in Texas, suggests the momentous transition may have occurred much later. He points out the Kargel's estimate was just a lower limit on when the change happened, because it did not include the effect of clouds in the Venusian atmosphere.
Clouds reflect sunlight back to space and therefore cool a planet's surface, and Grinspoon's preliminary calculations indicate that the effect can be dramatic - keeping the atmosphere 100 Kelvin cooler than without them.
Although more detailed modeling remains to be done, Grinspoon says the difference could mean that oceans and pleasant temperatures may have persisted on Venus for at least two billion years...................
CRUSHING atmospheric pressures, fierce winds, baking temperatures and acidic clouds have quickly destroyed every probe or lander ever sent to Venus. So the prospect of emulating the spectacular success of NASA's Mars rovers Spirit and Opportunity on Venus might seem bleak. But there is hope. Space scientists in the US believe a solar-powered aircraft could explore the atmosphere of the second rock from the sun, and carry a flying "brain" to control a toughened rover on the ground.
Writing in the latest edition of the journal Acta Astronautica (vol 56, p 750), a team led by Geoffrey Landis of NASA's Glenn Research Center in Ohio says that an autonomous solar-powered aircraft could cruise between different altitudes and locations in Venus's wild atmosphere, making measurements and radar-imaging the surface at 10 times the resolution possible with an orbiting craft. They say this would provide far better data than the Soviet and US probes of the 1970s and 1980s, which were only able to make atmospheric measurements for a short time as they descended to their doom in the planet's violent, corrosive winds.
But the planet's dense atmosphere is ideal for a flying craft. A wing's lift depends directly on the density of the atmosphere and the atmospheric pressure on Venus is about 90 times that of Earth. After being released by an orbiter, the craft's origami-like wings would unfurl from an "aeroshell" (see Graphic). Solar panels on the craft's surface could absorb large amounts of the intense solar energy, powering motors to allow the craft to fly continuously. And the planet's slow rotation, with one day and night on Venus taking 117 Earth days, means a solar flyer could stay on the daylight side indefinitely.
NASA is particularly interested in studying a fast-moving cloud band that stretches around the planet at an altitude of 50 to 75 kilometres. This band is an enigma. Amazingly, it spins 60 times faster than Venus itself, taking only four Earth days to circumnavigate the planet. "We really want to know how solar energy moves that upper atmosphere so very fast," Landis says. By cruising between the cloud base and cloud tops, where the temperature is a moderate 100 °C, a solar flyer could help scientists find out what makes that cloud band tick.
But down on the ground, where temperatures on the planet's day-side reach around 450 °C, a rover undertaking geological and imaging work would not last long. "We think we can get electrical things like motors and transistors to work at those temperatures, but not the microelectronics for computers," says Landis, who is also part of the science team running the Spirit and Opportunity missions.
His answer is to land a relatively dumb rover on the surface - which would be heat-proof, acid-proof and pressure-proof. The microchips that control the rover's motion, communication and imaging would be housed on the solar-powered flyer 50 kilometres above. "With no vulnerable on-board computer, we might then be able to duplicate the Spirit and Opportunity missions," Landis says. The down side would be the delay while the flying computer relays data to or from the dumb rover via a radio link.
Funding for such ambitious schemes is uncertain, with NASA having only recently acquired new administrator Michael Griffin. However, others welcome the idea of using an aircraft for atmospheric analysis on Venus. "An in situ mission in the clouds of Venus would be very welcome," says Colin Wilson of the University of Oxford, an expert in atmospheric dynamics with the European Space Agency's Venus Express mission, which launches in October.
Venus Express is a duplicate of ESA's Mars Express orbiter, which has sent back stunning images of the Martian surface. The new orbiter will use infrared instruments to study the deep atmosphere of Venus. "But we won't know exactly what's going on in the clouds without in situ measurements," says Wilson.
The European Space Agency is set to launch a spacecraft to Venus. It will be the first mission to the swelteringly hot and corrosive planet in 15 years.
Called Venus Express, it is scheduled to lift off aboard a Soyuz rocket from Baikonur, Kazakhstan, on 26 October. When it arrives at Venus in April 2006, it will study the planet from a polar orbit stretching from an altitude of 250 to 60,000 kilometres.
Seven instruments will scrutinise the planet at a range of wavelengths. Astronomers hope to understand how a planet that has more in common with Earth than any other in terms of distance from the Sun, size and mass could have evolved into such an inhospitable world.
Temperatures hover at 450°C, while the thick, carbon dioxide atmosphere produces crushing surface pressures 90 times those on Earth and sulphuric acid rains from the sky. "We're still struggling to understand why Venus is so radically different from Earth," says Fred Taylor, an astronomer at the University of Oxford, UK.
The mission will focus mainly on the composition and temperature of Venus's atmosphere. It rotates 50 to 60 times faster than the planet itself, which spins just once every 243 days and in the opposite direction to Earth. In particular, researchers will study mysterious hurricane-like vortices above the poles.
Mission scientists also hope to probe down to the surface, where the clouds are thinner. This thinning was discovered during a flyby of Venus with the Galileo spacecraft in 1990. Patches of near-infrared light seen on the planet's dark side were interpreted to be the planet's own heat glowing through relatively thin clouds. "The surface is so hot, it's effectively backlighting the thinner clouds," says Taylor.
The surface will also be scanned for active volcanism, hinted at by the presence of sulphuric acid in the atmosphere, but never seen. Venus boasts the most volcanoes of any planet in the solar system. Nearly 90% of its surface is covered by basaltic lava flows. Based on the size and number of impact craters, the lava appears to be about 500 million years old.
This age suggests that, unlike Earth, Venus does not have multiple rocky plates that constantly move and collide over the hot, soft rock in the planet's core. On Earth, plate tectonics enables heat to escape from the core.
Instead, Venus's surface may have been made of a single plate that was destroyed 500 million years ago when enough heat built up in the planet's interior. Such "catastrophic resurfacing" may be a cyclic process, says Dmitri Titov, a team member at the Max Planck Institute for Solar System Studies in Katlenburg-Lindau, Germany.
But local volcanic activity probably goes on all the time, says Taylor, and the gases belched out in the process would "go a long way toward explaining Venus's extreme climate".
ESA developed the €220-million-mission in just three years. This was possible as it is based largely on the design and instrumentation of the agency's Rosetta mission - currently on track to reach a comet in 2014 - and its Mars Express orbiter.
But this approach may also have drawbacks. For example, Venus Express carries a spectrometer called the PFS, which has recently failed on Mars Express. But Don McCoy, the mission's project manager, says the instrument probably stopped working because it simply wore out. He says Venus Express mission officials may carefully select the times when the PFS takes data "to make sure we don't use it up too soon".
The mission is the first dedicated to Venus since NASA's Magellan spacecraft mapped the surface of the planet in 1990. Venus Express is scheduled to operate for about 500 Earth days - the equivalent of two rotations of Venus - but it has enough fuel to last 1000 days.
The investigative tests on Europe's delayed Venus mission spacecraft are looking promising, say officials.
Wednesday's planned launch was postponed when contamination was found inside the Russian-made rocket.
Inspections show the spacecraft is in good condition and should be cleaned up within days, the European Space Agency (Esa) said.
A new launch date has yet to be set for the probe, but an Esa spokesperson said it would not be before 4 November.
The craft is due to blast off aboard a Russian rocket from Baikonur.
The launch was postponed on Friday when particles of contaminating material were discovered inside the rocket fairing.
The spacecraft had to be removed from the rocket and transported back into assembly buildings at the Kazakhstan spaceport.
Engineers began inspecting the damage on Monday and found that bits of the insulating material that protects the spacecraft inside the upper stage of the rocket had worked loose.
Esa spokesman, Franco Bonacina, said the contaminating material appeared to be confined to relatively large pieces that can be easily spotted and removed.
"It doesn't look like an enormous amount of material," he told the BBC News website. "It's relatively good news compared with what we knew on Saturday."
Once the clean-up operation is complete, the spacecraft, sitting on the top part of its rocket, will be moved out to the launch pad.
Esa is confident the probe will take off well within the launch window, which closes on 24 November this year.
The spacecraft will carry out the first global investigation of Venus' atmosphere, to shed light on how the planet evolved its harsh climate.
Composed chiefly of carbon dioxide, Venus' atmosphere generates intense greenhouse warming, whereby trapped solar radiation heats the surface of the planet to an average temperature of 467 Celsius.
Experts think Venus could teach us more about how the Earth's climate will respond to the release of greenhouse gases resulting from human activities.
Europe is all set to send a probe to Venus, the first mission to our nearest planetary neighbour in a decade.
Venus Express will launch on a Russian Soyuz rocket from Baikonur Cosmodrome in Kazakhstan at 0333 GMT on Wednesday.
The robotic craft will orbit the planet for about 500 Earth days to study its atmosphere, which has experienced runaway greenhouse warming.
Scientists hope the mission will shed further light on the mechanisms of climate change on our own world.
Venus is almost identical in size to Earth, and is thought to have a similar composition. But there the resemblance ends.
A dense, largely carbon dioxide, atmosphere acts as a blanket, trapping incoming solar radiation to heat the planet's surface to an average temperature of 467C (872F).
Surface pressure is about 90 times that on Earth. Several probes sent to land on Venus in the '60s were crushed before they could touch down.
Venus has turned out to be far less Earth-like than was expected. The planet's cloud layer is very reflective, absorbing much less heat from the Sun than our own planet does.
"The $64,000 question about the climate is why is it so different? Why is it so hot and why is the pressure so high?" proffered Fred Taylor of the University of Oxford, an interdisciplinary scientist on the mission.
By studying this hostile world, scientists hope to understand better how a warming future on our own planet might evolve.
"Venus provides an extreme test for the atmospheric physics models that we have for Earth," Andrew Coates, an investigator on the spacecraft's Aspera experiment, told the BBC News website.
Venus Express copies the basic structure of the highly successful Mars Express spacecraft, launched in 2003, and many of its science instruments. The mission has had a fast turnaround, taking just three years to put together.
Lift off from Baikonur was originally due on 26 October, but was postponed after insulating material from inside the rocket's fairing was found to have contaminated the orbiter.
This has been cleaned up and Venus Express is now back on the launch pad.
Following separation of the Soyuz rocket's three lower stages, an upper "Fregat" booster stage, with the probe mounted on top, will enter a sub-orbital trajectory.
With the aid of two burns, the Fregat stage will then hurl the spacecraft into an escape trajectory that takes it directly to Venus.
In about five months, Venus Express will reach its target and enter an elliptical polar orbit.
Accepted views of how the planet Venus evolved are challenged by new age dates for its surface.
Massive volcanism 500 million years ago was thought to have covered over much of the planet's ancient features.
But work carried out at Imperial College London, UK, suggests a "volcanic catastrophe" is not needed to explain the look of Venus's surface.
The British team presented details of its research to a major science conference in Texas, US.
Scientists will have an early opportunity to examine the new ideas - Europe's Venus Express spacecraft is due to arrive at the planet next month for a two-year investigation of Earth's near-neighbour.
Researchers date planetary surfaces by looking at the distribution of their impact craters.
On most planets and moons, impact craters tend to be clustered on very old parts of the surface, due to the heavy bombardment that is believed to have taken place in the early Solar System.
But craters on Venus are distributed randomly over the whole planet. This has led some scientists to the conclusion that most of the surface is of similar age.
One way to arrive at this result is by rapid resurfacing - the model long accepted by planetary scientists.
Timothy Bond and Mike Warner of Imperial College London have now thrown that theory into doubt.
Using computer modelling, they came up with a suite of possible scenarios that were compatible with the planet's cratering record and surface features.
They concluded that there was no need to invoke massive outpourings of lava over a short period. Instead, the planet's present-day surface could be compatible with a slow decline of volcanic activity, they argue.
"The transition from a high rate of resurfacing to a low rate could have lasted as long as two billion years," Timothy Bond told the BBC News website.
Professor Warner added: "We haven't shown that a very short event isn't possible, we've just shown that there are a much wider range of possibilities.
"A very short event is, a priori, quite unlikely given that there is a much wider range of likely realities."
Previous work suggests the volcanic upheaval 500 million years ago covered up "almost all" of the ancient surface.
The models developed at Imperial College suggest about 26% of the planet's surface could be older than 700 million years.
The findings agree with new models of heat loss from the interior of Venus produced by Dr Richard Ghail, also of Imperial College.
Earth's surface is divided into many plates that move relative to one another on convection currents in the mantle below.
At a type of boundary called a subduction zone, one plate is dragged down below an adjacent plate and destroyed in the mantle. At another, called a spreading ridge, two plates move apart and grow as volcanism adds new material at their edges.
These processes, called plate tectonics, continually cool the Earth and keep it in balance - what scientists call a "steady-state".
There is little evidence of plate tectonics on Venus. Therefore, some scientists think heat might build up below the Venusian crust, leading to occasional catastrophic releases of magma along with rapid resurfacing of the planet.
However, Dr Ghail believes the surface features of Venus do not necessarily reflect the rate of plate tectonics on the planet.
Instead, he thinks high temperatures in the interior create a weak zone between the crust and the mantle which essentially decouples, or separates, them from each other. This would allow more continual plate tectonic activity that would leave little evidence on the surface.
"I think we're moving closer towards a steady-state model for Venus," Dr Ghail told the BBC News website.
The researchers presented their results here at the Lunar and Planetary Science Conference in Houston, Texas.
European ground controllers say the Venus Express probe has successfully reached orbit around the planet.
At 0817 BST, they fired the main engine of the craft, slowing it enough for it to be captured by the planet's gravity.
Venus Express will orbit our nearest planetary neighbour for about 500 Earth days to study its atmosphere, which has undergone runaway greenhouse warming.
The mission should shed light on the mechanisms of climate change on Earth.
Tuesday's arrival marks the end of a five-month journey for the European Space Agency (Esa) mission.
Though it is closer to the Sun than our own planet, a thick, highly reflective cloud layer means Venus absorbs less solar radiation than the Earth. One might therefore expect surface conditions on the two planets to be similar.
But Venus' dense, largely carbon dioxide, atmosphere acts as a blanket, trapping incoming solar radiation to heat the planet's surface to an average temperature of 467C (872F) - hot enough to melt lead.
The mission aims to investigate how this world, so close to our own in size, mass, and composition, has evolved so differently over the last 4.6 billion years.
The main engine burn, which started at 0817 BST, was initiated by controllers at Esa's operations centre in Darmstadt, Germany.
It was designed to reduce the spacecraft's velocity relative to Venus by 15%, allowing it to drift into orbit around the planet.
Mike Healy, UK director for EADS-Astrium, the spacecraft's main contractor, said it was a critical manoeuvre.
"If it burns for too long you could end up crashing into the planet," he told the BBC News website.
At 0845 BST, with its engine still firing, Venus Express disappeared behind the planet, severing contact between the craft and Earth.
After about 10 minutes, controllers heard the spacecraft's signal - an early indication that the manoeuvre had worked and it was in orbit around Venus.
If all goes to plan, Venus Express will slip into a tight, elliptical orbit which will bring it to within 400km (250 miles) of the poles.
Its seven instruments will search for clues about why the planet has an atmosphere almost 90 times denser than Earth's and shrouded in clouds of sulphuric acid.
Although Earth is unlikely to ever end up as hot, a build-up of greenhouse gases in the atmosphere could result in our own planet taking some uncomfortable steps toward the situation on Venus.
Our planetary neighbour's hostile climate could also hold answers to how global warming will affect Earth in future decades, helping to constrain computer models of climate change.
"Our prime objective is to study the processes that are going on inside Venus' atmosphere," Gerhard Schwehm, Esa's head of planetary missions told the BBC News website.
"Nearly all the instruments give us information on either the composition of the atmosphere, temperature profile, or circulation. We want to see how the system works there because there are still many mysteries about Venus."
Mission scientists hope to learn what causes Venus' atmosphere to rotate much faster than the planet below. The craft will also study a swirling double vortex at the planet's north pole, to discover how it remains stable and where it gets its energy from.
Venus Express lifted off on a Russian Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan on 9 November 2005.
Probe peers into Venusian secrets
VIRTIS pulls back the layers
Venus is an enigma, wrapped in a mystery, inside a dense cloud of carbon dioxide (CO2).
But a suite of orbiting instruments is proving its ability to penetrate the thick atmosphere and create a new and dynamic picture of Earth's sister planet.
Scientists at the Division of Planetary Sciences meeting in Pasadena, California, this week said that data streaming from the Venus Express probe had provided unprecedented detail of the Venusian atmosphere and the first-ever peek at its lower strata.
They hope the spacecraft will help answer fundamental questions about the planet's atmospheric composition and dynamics, as well as solve key Venus puzzles: what drives its "super-rotation"; are its volcanoes active; and just what is the strange ultraviolet-absorbing substance swirling at the cloud tops?
From what we have now, this will be like going from a 19th Century topographical map to the Weather Channel
David Grinspoon, mission scientist
But for now, scientists are happy to report that all the instruments are in good working order and beaming back massive amounts of data.
"It's a treasure trove of information," said David Grinspoon, a participating scientist with the mission, "and we've barely opened the chest and looked in."
The seven instruments on the spacecraft, in obit around Venus since April, are examining the planet over a wide swath of the spectrum: from ultraviolet to visible, to infrared, and even radio wavelengths.
"Our main objective is to do a comprehensive study of the atmosphere," said Hakan Svedhem, Venus Express project scientist.
The instruments provide a look at Venus at different depths.
The Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS), for example, allows scientists to penetrate the otherwise opaque upper atmosphere of Venus and study the chemistry below it.
It takes advantage of "infrared windows", the few narrow wavelengths that carbon dioxide does not absorb.
"It's like looking through gaps in a picket fence for the first time and seeing through," said Dr Grinspoon.
Unlike Mars, Venus is a close planetary neighbour of Earth that remains relatively unexplored.
The dense atmosphere has shielded it from scrutiny, but scientists speculate that Venus once had vast oceans, similar to Earth. The oceans have since disappeared.
"The closest analogy to Venus today is the Achaean Earth, prior to life, when Earth's atmosphere was primarily CO2 and a lot of sulphur," said Frank Mills, a supporting investigator on the mission.
Scientists want to understand the evolutionary divergence of the sister planets - what happened to the oceans on Venus, and what triggered its runaway greenhouse?
Some clues may be found in understanding the role and amount of sulphur dioxide (SO2) in the atmosphere, said Dr Mills. When oxidised, it produces sulphuric acid, the main component of Venusian clouds and a tremendous greenhouse gas.
The gas is also a product of volcanoes. Previous measurements of Venus from ground-based instruments and the Pioneer spacecraft have showed a spike of sulphur dioxide followed by a gradual decrease, suggesting that the planet's volcanoes are not dormant.
But the last measurements of SO2 were 20 years ago. VIRTIS will provide a long-needed update.
Meanwhile, the Visible Monitoring Camera (VMC) may solve another Venusian mystery.
The VMC produces visible and ultraviolet images of the planet. In the visible range, the Venus surface remains opaque. But in the ultraviolet, a swirling weather pattern appears. It is unclear what it is made of. Some guess an aerosol or small crystals.
"It is some substance absorbing the ultraviolet, that's not CO2," said Dr Svedhem.
"People have tried to identify it and have failed, and it's really strange," added Dr Grinspoon; "it's dubbed the 'unknown ultraviolet absorber'. "
As if the composition of the Venusian atmosphere is not intriguing enough, scientists hope Venus Express will also help explain why it is spinning faster than the planetary body beneath it.
While winds on Earth flow in Easterly and Westerly directions, on Venus they seem to flow only Eastward, and at speeds faster than the planet's rotation.
The double vortex viewed by VIRTIS (Esa)
VIRTIS sees a peculiar double-eye vortex structure at the south pole
Scientists don't know what's causing the super-rotation, or even how to describe it.
"Is it contributing to the planet's spin? Why doesn't it break down?" pondered Sanjay Limaye, a planetary scientist with the mission. "We just don't know."
He is pleased by the new images that VIRTIS has returned of the double vortex that sits like twin cyclones at the eye of the southern hemispheric circulation.
"Venus Express can help us define the depth and the structure of the vortex, and how the whole circulation is maintained," said Dr Limaye.
As Venus Express continues to beam back data over the next few years, scientists will create a new dynamic map of the planet's once impenetrable atmosphere.
"From what we have now, this will be like going from a 19th Century topographical map to the Weather Channel," said Dr Grinspoon.
Venus may have had continents and oceans
Granite highlands point to past water — and perhaps life.
Venus's atmosphere is 96% carbon dioxide, with clouds of sulphuric acid.NASAThe planet Venus, now hellishly hot and dry, may have once have been far more like Earth, with oceans and continents. That is the implication of new research claiming to see evidence for granite highlands on the planet in data almost two decades old.
In 1990, NASA's Galileo spacecraft detected nighttime infrared emissions coming from Venus' surface. Analysing these data, an international team led by planetary scientist George Hashimoto, now at Okayama University, Japan, found that Venus's highland regions emitted less infrared radiation than its lowlands.
One interpretation of this lower infrared emission from the highlands, say the authors, is that they are composed largely of 'felsic' rocks, particularly granite. Granite, which on Earth is found in continental crust, requires water for its formation. The results are published in the Journal of Geophysical Research1.
"This is the first direct evidence that early in the history of the Solar System, Venus was a habitable planet with plenty of water," says Dirk Schulze-Makuch, an astrobiologist at Washington State University in Pullman, who was not involved in the study. "The question is how long Venus remained habitable. But this gives new impetus for the search for microbial life in Venus's lower atmosphere."
Before Galileo, researchers had believed that only radar could see through the dense clouds of sulphuric acid in Venus's atmosphere to the surface, says co-author Kevin Baines, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "Detecting the surface in the infrared is a breakthrough," he says.
The interpretation of such measurements, however, hinges on disentangling the effects of Venus's thick atmosphere. Not everyone is convinced that Hashimoto's team has achieved this.
David Crisp, also at NASA's Jet Propulsion Laboratory, has studied the atmospheres of various planets. Crisp, who was not involved in this latest analysis, spent several years attempting such detections using similar data. These new conclusions aren't supported either by the available data or the team's own models, he says.
"We understand our paper doesn't resolve everything," responds co-author Seiji Sugita, a planetary scientist at the University of Tokyo. Sugita says the next step is to apply their models to data from the European Space Agency's Venus Express spacecraft, which is already orbiting Venus, and the Japanese Space Agency's Venus Climate Orbiter, scheduled for launch in 2010.
The possible presence of granite also suggests that tectonic plate movement and continent formation may have occurred on Venus, as well as recycling of water and carbon between the planet's mantle and atmosphere. The implication of continent formation is "quite significant", says geophysicist Norm Sleep of Stanford University in California.
Venus might have once been almost entirely underwater, says Sleep — although without further geochemical data, he adds, we don't know whether this early ocean's temperature was 30 ºC or 150 ºC.
Whether tepid or boiling, he says, any ocean on Venus would have lasted only a few hundred million years. As the Sun became hotter and brighter, the planet experienced a runaway greenhouse effect. Nowadays, the planet is a paragon of the uninhabitable, with an atmosphere of 96% carbon dioxide and a surface temperature of around 460 ºC.
"Any life on Venus that hadn't figured out how to colonize the cloud tops a billion years after the planet's formation would have been in big trouble," says Sleep.
Hashimoto, G. L., et al. J. Geophys. Res. 113, E00B24 (2008).
| Article | http://dx.doi.org/10.1029/2008JE003134
Perhaps that will happen to us when we've turned all the fossil fuel into CO2...amester said:If there were intelligent beings, perhaps any traces of their civilization melted away when the planet heated up to 800 degrees Fahrenheit. :shock:
eburacum said:At a certain level in Venus' atmosphere the environment is surprisingly clement. 50 km above the surface the temperature and pressure are both Earth-like, the most Earth-like conditions in the Solar System (according to Geoffrey Landis). Perhaps some lifeforms can persist there.
Of course the atmosphere at that level has no free oxygen and almost no water, but you can't have everything...