Surprise from the Lava Lake at Antarctica’s Erebus

image: The lava lake at Antarctica’s Erebus, seen in December 2011. credit: Clive Oppenheimer / Volcanofiles.

Lava lakes are a relatively rare volcanic features — there are only a handful of active ones on the planet. Kilauea (with two), Ambrym, Villarrica, Nyiragongo, Erta’Ale, a fairly new, possibly ephemeral lake at Tolbachik and probably the most remote lava lake of them all, Erebus in Antarctica. The Erebus lava lake as been a persistent feature on the volcano for decades (if not longer). However, it’s remote location means it is normally monitored by satellite unless conditions allow for a team to reach the summit of the volcano from McMurdo Station (see above). As the southern hemisphere begins to head into fall, just such an opportunity came last week, so geologists from McMurdo set off to view the lava lake.

What they found took everyone by surprise (including me). It has long been thought that life arose around volcano features like active vents and thermal features — we’ve seen clear documentation of all sorts of life around black smokers around Antarctica and even bacteria living in very hot vents in places like the Yellowstone caldera. However, life in a place like Erebus has never been documented before. Dr. Julian Bashir from the US Antarctic Survey said it best: “as we descended the slope towards the Erebus lava lake, we were all struck by the strange sounds that were emanating from the crater. The haze of steam and volcanic gases finally lifted as the wind shifted some and much to our amazement, we could see something actually moving around on the lava lake!” The team was only able to take a few quick shots of before conditions worsened, but if this sighting proves to be true, our understanding of how life arose on our planet — and others in the solar system — could be changed forever.

Where Will Doomed Earth’s Last Organisms Live?

image 1: This artist’s impression shows a red giant engulfing a Jupiter-like planet as it expands.
image 2: Ice caves could be a final abode for microbial life in a far-future Earth with horrendous surface temperatures.

Billions of years from now, life on Earth will be extinguished when the dying sun scorches the surface of our planet. New research has aimed to determine what the last life forms on Earth will be, and what kind of abodes they will cling to before the Earth becomes sterilized.

We are fortunate that our planet orbits a star that has a long main-sequence lifetime. However, the sun’s luminosity is gradually increasing, and in about one billion years the effects of this will start to be felt on Earth.

Surface temperatures will start to creep relentlessly upwards over the next few billion years, which will increase the amount of water vapor in the air. This will act to further increase temperatures and will thus signify the beginning of the end for life on Earth.

The rising temperatures will cause excessive amounts of rain and wind, and thus increase the weathering of silicate rocks, which will suck extra carbon from the atmosphere.

Ordinarily, the carbon is replaced via plate tectonics in the carbon-silicate cycle as it is released in volcanic gases. However, the oceans will start to evaporate as the temperatures continue to rise, which will probably put a stop to plate tectonics as scientists believe that water is an essential lubricant for the motion of tectonic plates on Earth. This will deplete the number of active volcanoes, and the carbon will not be replenished in the atmosphere.

The lack of carbon dioxide will effectively choke plant life on Earth, since plants require atmospheric CO2 for their respiration. The death of oxygen-producing plants will in turn lead to less oxygen in the atmosphere over a few million years. This will spell disaster for the remaining animal life on Earth, with mammals and birds being the first to become extinct. Fish, amphibians and reptiles would survive a little longer, as they need less oxygen and have a greater tolerance to heat.

The last type of animal present on the far-future Earth would likely be invertebrates. Once the insects finally succumb to the increasing temperatures, the Earth will once again be solely populated by microbial life, just as it had been for the first few billion years of our planet’s history. The last lingering life will desperately seek out niches of the planet that are still habitable, but even extremophile forms of life will find this to be a challenge.

A habitable niche in an inhospitable world
As the Earth’s oceans evaporate, the few remaining pools of water could provide a last refuge for some microbes. The present average depth of the oceans is 2.5 miles (4 kilometers), but this extends to 6.8 (11 km) in the Mariana Trench, which is the deepest known ocean trench.

Trenches carved in the sea bed could be among the last places to harbor liquid water, with the looming walls offering some source of shade from the unforgiving sun. However, this potential haven is not quite as inviting as it may first seem. Air moving into the trench will become compressed as it sinks lower, and this pressure will greatly increase the air temperature above the water.

“By the time we get to the point where there’s a trench with a small pool of water at the bottom, a large mass of ocean water would have evaporated, so surface temperatures on the planet would be rapidly increasing,” said Jack O’Malley-James of the University of St. Andrews, and lead author of the new study. “Therefore, water at the bottom of a trench wouldn’t remain cool enough for long enough to make a good refuge for life.”

Another potential haven for the last microbial life on Earth could be in underground caves. Microbes have been found living in caves on the present-day Earth without any need for sunlight. Most caves in the far-future Earth would not be suitable for life, as temperatures increase with depth. However, caves that have large chambers below a narrow entrance might be colder, as the dense cold air is sucked in, but lighter warmer air is barricaded out.

Such caves are formed from collapsed lava tubes, and the cold air in the caves will cause in-falling snow to compact into ice during the winter, as well as freeze any incoming water. When the outside temperature climbs again, the cold air is still trapped within the cave, along with the ice. However, the ice will melt eventually as heat is conducted through the walls of the cave, so it must be continually replaced and therefore some source of water would still be necessary on the far-future Earth for such a cave to retain its cool climate.

Life could also exist in subsurface environments other than ice caves. Microbial life today has been found at depths of 3.3 miles (5.3 km) below the Earth’s surface. The increase of temperature with depth is around 86 degrees Fahrenheit (48 degrees Celsius) per mile (1.6 km); however, the exact increase depends on the type of rock. Such a subsurface refuge could be one of the last to contain life on Earth.

At the other end of the scale, temperatures will decrease by around 18.9 degrees Fahrenheit (10.5 degrees Celsius) per mile above the Earth’s surface. This is because the surface of the Earth re-radiates heat that has been received from the sun, thus heating the lower atmosphere.

The lower temperatures at high altitude would encourage microbial life on the far-future Earth to reach for the skies and seek refuge in the last remaining lakes in the mountains in an attempt to escape the heat. However, as tectonic plates cease to crash into each other, there will no longer be a force to drive mountains upwards. Instead, the mountains will succumb to weathering and eventually there will be fewer regions of high altitude on the planet.

The remaining high-altitude regions would likely be comprised of volcanoes, as convection of molten rock in the mantle of the Earth will still occur even after the cessation of plate movement. The lack of plate tectonics will allow these “hot spot” volcanoes to reach heights that are currently impossible to achieve today.

“Sites around active volcanoes on Earth today host life, so living near an active volcano shouldn’t be a challenge for extremophilic microorganisms,” said O’Malley-James. “It’s likely that volcanic activity would decline as the planet cools, but it may not stop completely during the time period in which planet is still habitable.”

Isolated pools from the remnants of the ocean will have high salt concentrations, meaning that bacterial life would have to withstand high saline as well as high temperatures. Such microbes are called thermohalophiles, and they exist today in such conditions around hydrothermal vents. Microbes on the far-future Earth would also have to contend with being bombarded with high doses of ultraviolet radiation, as the ozone layer would have been stripped away when the oxygen in the atmosphere diminished.

Biosignatures of a dying planet
Studying what life will be like on Earth at the end of the habitable era helps scientists narrow down what kind of biosignatures might exist on Earth-like exoplanets orbiting aging stars near the end of their main sequence. So what kind of biosignatures would the last life on Earth exhibit?

Thermohalophiles, such as those found at volcanoes in Chile’s Atacama Desert, use carbon monoxide to obtain energy, and the by-products of their metabolic processes include carbon dioxide, hydrogen, and ethanol.

Carbon dioxide could be seen as an indicator of life, considering that the carbon dioxide inherent to the planet would have been severely reduced million of years previously. Carbon dioxide by itself is not a biosignature and its presence, such as on Mars, does not indicate that life exists on a planet. However, biologically produced carbon dioxide would cause a disequilibrium of the CO2 in the atmosphere that could reveal the presence of microbial life.

Similarly, the biological production of hydrogen by the thermohalophiles could create an excess of hydrogen in the atmosphere, which could be used as an indicator of life. However, all of these biosignatures would likely be weak, as biological productivity would be severely diminished in a dying world.

Microbes can adapt to extreme conditions, such as the harsh conditions that existed on the early Earth. The first life to appear on Earth, as far back as 3.8 billion years ago, was unicellular life. Similarly, microbes will be the sole occupants of the Earth during its final days as a habitable planet. Microbial biospheres would exhibit biosignatures that are very dissimilar to what is present on the current Earth, but whether late-type biospheres would appear similar to early-type biospheres is another question.

“It looks like they would be similar to the biosignatures for early-type microbial biospheres, but the strength of the various atmospheric signatures would be much lower for the late-type microbial biospheres,” said O’Malley-James. “So it may be possible to distinguish between early and late microbial biospheres purely by looking at the strength of the various biosignature gases in the atmospheric spectra of Earth-like planets.”

Future work will seek to refine what these biosignatures could be, and ultimately search for the telltale signs of a dying habitable planet among the Earth-like planets that have been discovered so far.

The paper has been published in the International Journal of Astrobiology. The preprint can be found here: http://arxiv.org/abs/1210.5721

Deep-Sea Mining Is Closer Than You Think

image: Yeti crabs crowd the newly discovered hydrothermal vent ecosystem near Antarctica. (Image: NERC ChEsSo Consortium)

Late last year, hydrothermal vents were discovered around Antarctica, carpeted with thousands of ghost-white yeti crabs. In January, a different expedition identified what may be the hottest hydrothermal vents on Earth along the Mid-Cayman Rise, where amagmatic spreading allows heat from the mantle to reach the surface of the oceanic crust. And in April, deep-sea researchers discovered an exotic new type of underwater volcano – one made of rhyolite rock rather than basalt, which could form the basis for a unique biological community.

The exploratory investigation of the deep ocean is clearly a vibrant and quickly developing line of work, but even as scientists continue to catalog the full range of biological and geological diversity, mining companies are ramping up plans to extract minerals from deep-sea deposits.

Nautilus Minerals Inc. was just weeks away from starting production near the Solwara 1 hydrothermal vents off the coast of Papua New Guinea, where metal-rich fluids spew into the ocean and form mineral deposits. A financial dispute with the government over each partner’s equity stake has postponed the endeavor.

Many environmentalists, skeptical of the project’s environmental impact statement, were assuaged by the news, but the financial bickering may only be delaying the inevitable as an international field of resource-hungry competitors jockeys for position. India has dialed in on a portion of the Central Indian Ocean Basin, a Saudi-Sudanese joint venture is preparing for Red Sea mining, and Germany has prioritized technology development for deployment around the world.

Deep-sea mining is poised as a major growth industry over the next decade, as large developing-world populations drive consumer demand for metal-containing products, climate change makes previously inaccessible regions like the Arctic Ocean seabed attainable, and improved extraction technologies turn previously uneconomical rock into paydirt.

Cindy Van Dover is a Professor of Biological Oceanography at Duke University and a leading voice in the development of policy and management strategies for deep-sea extraction activities. Van Dover has studied the ecology of hydrothermal vents for years, and she takes a measured, pragmatic approach to the coming industrialization of her study sites. If mining is going to happen – a event that the more strident faction of the environmental movement will no doubt contest – “we need to work with industry to make sure we do it right,” says Van Dover.

One place for scientists to take an active role is in communicating the full value of deep-sea communities. “Because it is out of sight and outside the daily experience of most people,” explains Van Dover, “it is hard for the general public to value the deep-sea environment. Getting more and better numbers on the goods and services provided by deep-sea ecosystems could really be useful.”

Indeed, if done properly, the industrialization of the deep-sea could actually be a boon to science. Responsible use of these resources – and to be clear, our metals must come from somewhere – would require that we understand the full ecological impact on hydrothermally derived systems. Characterization expeditions in advance of mining operations could vastly expand our knowledge of certain applied parameters such as mineral deposition rates and “how to maintain critical population levels to ensure the survival of species that naturally occur in a region,” as Van Dover puts it.

Until the legal framework of mining in international waters catches up to the ready-to-dig reality, cooperative participation from scientists may be the best way to preserve the most fragile, irreplaceable aspects of deep-sea ecosystems.

Recent developments have highlighted the rapidly moving nature of this expanding frontier, and all parties – scientists, miners, and conservationists – will need to keep up. “Deep-sea conservation is something I never thought I’d have to deal with in my career,” admits Van Dover. “I assumed human activities and impacts in the deep sea were decades, if not centuries into the future.”

In an Isolated, Ice-Covered Antarctic Lake Far Below Freezing, Life is Found

image (main): Lake Vida lies within one of Antarctica’s cold, arid McMurdo Dry Valleys (Photo: Desert Research Institute)

Even inside an almost completely frozen lake within Antarctica’s inland dry valleys, in dark, salt-laden and sub-freezing water full of nitrous oxide, life thrives… offering a clue at what might one day be found in similar environments elsewhere in the Solar System.

Researchers from NASA, the Desert Research Institute in Nevada, the University of Illinois at Chicago and nine other institutions have discovered colonies of bacteria living in one of the most isolated places on Earth: Antarctica’s Lake Vida, located in Victoria Valley — one of the southern continent’s incredibly arid McMurdo Dry Valleys.

These organisms seem to be thriving despite the harsh conditions. Covered by 20 meters (65 feet) of ice, the water in Lake Vida is six times saltier than seawater and contains the highest levels of nitrous oxide ever found in a natural body of water. Sunlight doesn’t penetrate very far below the frozen surface, and due to the hypersaline conditions and pressure of the ice water temperatures can plunge to a frigid -13.5 ºC (8 ºF).

Yet even within such a seemingly inhospitable environment Lake Vida is host to a “surprisingly diverse and abundant assemblage of bacteria” existing within water channels branching through the ice, separated from the sun’s energy and isolated from exterior influences for an estimated 3,000 years.

Originally thought to be frozen solid, ground penetrating radar surveys in 1995 revealed a very salty liquid layer (a brine) underlying the lake’s year-round 20-meter-thick ice cover.

“This study provides a window into one of the most unique ecosystems on Earth,” said Dr. Alison Murray, one of the lead authors of the team’s paper, a molecular microbial ecologist and polar researcher and a member of 14 expeditions to the Southern Ocean and Antarctic continent. “Our knowledge of geochemical and microbial processes in lightless icy environments, especially at subzero temperatures, has been mostly unknown up until now. This work expands our understanding of the types of life that can survive in these isolated, cryoecosystems and how different strategies may be used to exist in such challenging environments.”

Sterile environments had to be set up within tents on Lake Vida’s surface so the researchers could be sure that the core samples they were drilling were pristine, and weren’t being contaminated with any introduced organisms.

According to a NASA press release, “geochemical analyses suggest chemical reactions between the brine and the underlying iron-rich sediments generate nitrous oxide and molecular hydrogen. The latter, in part, may provide the energy needed to support the brine’s diverse microbial life.”

“This system is probably the best analog we have for possible ecosystems in the subsurface waters of Saturn’s moon Enceladus and Jupiter’s moon Europa.”
– Chris McKay, co-author, NASA’s Ames Research Center

What’s particularly exciting is the similarity between conditions found in ice-covered Antarctic lakes and those that could be found on other worlds in our Solar System. If life could survive in Lake Vida, as harsh and isolated as it is, could it also be found beneath the icy surface of Europa, or within the (hypothesized) subsurface oceans of Enceladus? And what about the ice caps of Mars? Might there be similar channels of super-salty liquid water running through Mars’ ice, with microbes eking out an existence on iron sediments?

“It’s plausible that a life-supporting energy source exists solely from the chemical reaction between anoxic salt water and the rock,” explained Dr. Christian Fritsen, a systems microbial ecologist and Research Professor in DRI’s Division of Earth and Ecosystem Sciences and co-author of the study.

“If that’s the case,” Murray added, “this gives us an entirely new framework for thinking of how life can be supported in cryoecosystems on earth and in other icy worlds of the universe.”

More research is planned to study the chemical interactions between the sediment and the brine as well as the genetic makeup of the microbial communities themselves.

The research was published this week in the Proceedings of the National Academy of Science (PNAS).

Funding for the research was supported jointly by NSF and NASA. Images courtesy the Desert Research Institute. Dry valley image credit: NASA/Landsat. Europa image: NASA/Ted Stryk.)

underhelios:

Deinococcus radiodurans is an extremophilic bacterium, one of the most radioresistant organisms known. It can survive cold, dehydration, vacuum, and acid, and is therefore known as a polyextremophile and has been listed as the world’s toughest bacterium in The Guinness Book Of World Records.

http://en.wikipedia.org/wiki/Deinococcus_radiodurans

(via scinerds)