Posted on by Paul Scott Anderson

How Plants May Have Helped Create Earth’s Unique Landscapes

Credit: Wikimedia Commons

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According to conventional thinking, plant life first took hold on Earth after oceans and rivers formed; the soil produced by liquid water breaking down bare rock provided an ideal medium for plants to grow in. It certainly sounds logical, but a new study is challenging that view – the theory is that vascular plants, those containing a transport system for water and nutrients, actually created a cycle of glaciation and melting, conditions which led to the formation of rivers and mud which allowed forests and farmland to later develop. In short, they helped actually create the landscapes we see today.

The evidence was just published in two articles in a special edition of Nature Geoscience.

In the first article, analysis of the data proposes that vascular plants began to absorb the carbon dioxide in the atmosphere about 450 million years ago. This led to a cooling of temperatures on a global scale, resulting in widespread glaciation. As the glaciers later started to melt, they ground up the Earth’s surface, forming the kind of soils we see today.

The second article goes further, stating that today’s rivers were also created by vascular plants – the vegetation broke the rocks down into mud and minerals and then also held the mud in place. This caused river banks to start forming, acting as channels for water, which up until then had tended to flow over the surface much more randomly. As the water was channeled into more specific routes, rivers formed. This led to periodic flooding; sediments were deposited over large areas which created rich soil. As trees were able to take root in this new soil, debris from the trees fell into the rivers, creating logjams. This had the effect of creating new rivers and causing more flooding. These larger fertile areas were then able to support the growth of larger lush forests and farmland.

According to Martin Gibling, a professor of Earth science at Dalhousie University, “Sedimentary rocks, before plants, contained almost no mud. But after plants developed, the mud content increased dramatically. Muddy landscapes expanded greatly. A new kind of eco-space was created that wasn’t there before.”

The new theory also leads to the possibility that any exoplanets that happen to have vegetation would look different from Earth; varying circumstances would create a surface unique to each world. Any truly Earth-like exoplanets might be very similar in general, but the way that their surfaces have been modified might be rather different.

It’s an interesting scenario, but it also raises other questions. What about the ancient river channels on Mars? Some appear to have been formed by brief catastrophic floods, but others seem more similar to long-lived rivers here on Earth, especially if there actually was a northern hemisphere ocean as well. How did they form? Does this mean that rivers could form in a variety of ways, with or without plant life being involved? Could Mars have once had something equivalent to vascular plant life as well? Or could the new theory just be wrong? Then there’s Titan, which has numerous rivers still flowing today. Albeit they are liquid methane/ethane instead of water, but what exactly led to their formation?

From the editorial in Nature Geoscience:

Without the workings of life, the Earth would not be the planet it is today. Even if there are a number of planets that could support tectonics, running water and the chemical cycles that are essential for life as we know it, it seems unlikely that any of them would look like Earth. Even if evolution follows a predictable path, filling all available niches in a reproducible and consistent way, the niches on any Earth analogue could be different if the composition of its surface and atmosphere are not identical to those of Earth. And if evolution is random, the differences would be expected to be even larger. Either way, a glimpse of the surface of an exoplanet — if we ever get one — may give us a whole new perspective on biogeochemical cycling and geomorphology.

Just as the many exoplanets now being found are of a previously unknown and amazingly wide variety, and all uniquely alien, even the ones that (may) support life are likely to be just as diverse from each other as they are from Earth itself. Earth’s “twin” may be out there, but in terms of outward appearance, it may be somewhat more of a fraternal twin than an exact replica.

Posted on by Amy Shira Teitel

Looks Like We’re Still Looking for Earthly Life Forms on Other Planets

GFAJ-1, the bacterium found in California's Lake Mono. Image credit: Science/AAAS

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In late 2010, NASA set the Internet buzzing when it called a press conference to discuss an astrobiological finding that would impact the search for extraterrestrial life. Many speculated that some primitive life had been found on Mars or one of Saturn’s moons. But the evidence was found on Earth; a strain of bacteria in California’s Lake Mono that had arsenic in its genetic structure. The discovery implied that life could thrive without the elements NASA typically looks for, mainly carbon and phosphorous. But now, a new study challenges the existence of arsenic-based life forms. 

The 2010 paper announcing arsenic based life, “Arsenic-eating microbe may redefine chemistry of life,” was written by a team of scientists led by Felisa Wolfe-Simon. The paper appeared in Science and refuted the long-held assumption that all living things need phosphorus to function, as well as other elements including carbon, hydrogen, and oxygen.

Lake Mono, as seen from Space. Image credit: NASA

The phosphate ion plays several essential roles in cells: it maintains the structure of DNA and RNA, it combines with lipids to make cell membranes, and it transports energy within the cell through the molecule adenosine triphosphate (ATP). Finding a bacteria that uses normally poisonous arsenic in the place of phosphate shook up the guidelines that have structured NASA’s search for life on other worlds.

But microbiologist Rosie Redfield didn’t agree with Wolfe-Simon’s article and published her concerns as technical comments in subsequent issues of Science. Then, she put Wolfe-Simon’s results to the test. She led a team of scientists at the University of British Columbia in Vancouver and tracked her progress online in the name of open science.

Redfield followed Wolfe-Simon’s procedure. She grew GFAJ-1 bacteria, the same strain found in Lake Mono, in a solution of arsenic with a very small amount of phosphorus. She then purified DNA from the cells and sent the material to Princeton University in New Jersey. There, graduate student Marshall Louis Reaves separated the DNA into fractions of varying densities using caesium chloride centrifugation. Caesium chloride, a salt, creates a density gradient when mixed with water and put in a centrifuge. Any DNA in the mixture will settle throughout the gradient depending on its structure. Reaves studied the resulting DNA gradient using a mass spectrometer to identify the different elements at each density. He found no trace of arsenic in the DNA.

Redfield’s results aren’t by themselves conclusive; one experiment isn’t enough to definitively disprove Wolfe-Simon’s arsenic-life paper. Some biochemists are eager to continue the research and want to figure out the lowest possible level of arsenic that Redfield’s method could detect as a way of determining exactly where arsenic from the GFAJ-1 DNA ends up on a caesium chloride gradient.

Dr. Redfield. Image credit: M. Dee/Nature

Wolfe-Simon is also not taking Redfield’s results as conclusive; she is still looking for arsenic in the bacterium. “We are looking for arsenate in the metabolites, as well as the assembled RNA and DNA, and expect others may be doing the same. With all this added effort from the community, we shall certainly know much more by next year.”

Redfield, however, isn’t planning any follow-up experiments to support her initial findings. “What we can say is that there is no arsenic in the DNA at all,” she said. “We’ve done our part. This is a clean demonstration, and I see no point in spending any more time on this.”

It’s unlikely that scientists will conclusively prove or disprove the existence arsenic-based life anytime soon. For the time being, NASA will likely confine its search for extraterrestrial life to phosphorus-dependent forms we know exist.

Source: nature.com

Posted on by Paul Scott Anderson

Key Step in Evolution Replicated by Scientists – With Yeast

Sacharomyces cerevisiae yeast cells. Credit: Wikimedia Commons

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One of the great puzzles in science has been the evolution of single-celled organisms into the incredibly wide variety of flora and fauna that we see today. How did Earth make the transition from an initially lifeless ball of rock to one populated only by single-celled organisms to a world teeming with more complex life?

As scientists understand it, single-celled organisms first began evolving into more complex forms more than 500 million years ago, as they began to form multi-cellular clusters. What isn’t understood is just how that process happened. But now, biologists are another step closer figuring out this puzzle, by successfully replicating this key step – using an ingredient common in the making of bread and beer – ordinary Brewer’s yeast (Saccharomyces cerevisiae). While helping to solve evolutionary riddles here on Earth, it also by extension has bearing on the question of biological evolution on other planets or moons as well.

The results were published in last week’s issue of the Journal Proceedings of the National Academy of Sciences (PNAS).

Yeasts are a microscopic form of fungi; they are uni-cellular but can become multi-cellular through the formation of a string of connected budding cells, like in molds. The experiments were based on this fact, and were surprisingly simple, they just hadn’t been done before, according to Will Ratcliff, a scientist at the University of Minnesota (UMN) and a co-author of the paper. “I don’t think anyone had ever tried it before,” he said, adding: “There aren’t many scientists doing experimental evolution, and they’re trying to answer questions about evolution, not recreate it.”

Sam Scheiner, program director in NSF’s Division of Environmental Biology, also adds: “To understand why the world is full of plants and animals, including humans, we need to know how one-celled organisms made the switch to living as a group, as multi-celled organisms. This study is the first to experimentally observe that transition, providing a look at an event that took place hundreds of millions of years ago.”

It’s been thought that the step toward multi-cellular complexity was a difficult one, an evolutionary hurdle that would be very hard to overcome. The new research however, suggests it may not be that difficult after all.

It took the first experiment only 60 days to produce results. The yeast was first added to a nutrient-rich culture, then the cells were allowed to grow for one day. They were then stratified by weight using a centrifuge. Clusters of yeast cells landed on the bottom of the test tubes. The process was then repeated, taking the cell clusters and re-adding them to fresh cultures. After sixty cycles of this, the cell clusters started to look like spherical snowflakes, composed of hundreds of cells.

The most significant finding was that the cells were not just clustering and sticking together randomly; the clusters were composed of cells that were genetically related to each other and remained attached after cell division. When clusters reached “critical mass,” some cells died, a process known as apoptosis, which allows the offspring to separate.

This then, simply put, is the process toward multi-cellular life. As described by Ratcliff, “A cluster alone isn’t multi-cellular. But when cells in a cluster cooperate, make sacrifices for the common good, and adapt to change, that’s an evolutionary transition to multi-cellularity.”

So next time you are baking bread or brewing your own beer, consider the fact that those lowly little yeast cells hold a lot more importance than just a useful role in your kitchen – they are also helping to solve some of the biggest mysteries of how life started, both here and perhaps elsewhere.

Posted on by Amy Shira Teitel

What if the Earth had Two Moons?

The Earth and Moon as seen from Mariner 10 en route to Venus. This could be a similar view of two moons as seen from Earth. Image credit: NASA/courtesy of nasaimages.org

The idea of an Earth with two moons has been a science fiction staple for decades. More recently, real possibilities of an Earth with two moons have popped up. The properties of the Moon’s far side has many scientists thinking that another moon used to orbit the Earth before smashing into the Moon and becoming part of its mass. Since 2006, astronomers have been tracking smaller secondary moons that our own Earth-Moon system captures; these metre-wide moons stay for a few months then leave.

But what if the Earth actually had a second permanent moon today? How different would life be? Astronomer and physicist Neil F. Comins delves into this thought experiment, and suggests some very interesting consequences. 

This shot of Io orbiting Jupiter shows the scale between other moons and their planet. Image credit:NASA/courtesy of nasaimages.org

Our Earth-Moon system is unique in the solar system. The Moon is 1/81 the mass of Earth while most moons are only about 3/10,000 the mass of their planet. The size of the Moon is a major contributing factor to complex life on Earth. It is responsible for the high tides that stirred up the primordial soup of the early Earth, it’s the reason our day is 24 hours long, it gives light for the variety of life forms that live and hunt during the night, and it keeps our planet’s axis tilted at the same angle to give us a constant cycle of seasons.

A second moon would change that.

For his two-mooned Earth thought experiment, Comins proposes that our Earth-Moon system formed as it did — he needs the same early conditions that allowed life to form — before capturing a third body. This moon, which I will call Luna, sits halfway between the Earth and the Moon.

Luna’s arrival would wreak havoc on Earth. Its gravity would tug on the planet causing absolutely massive tsunamis, earthquakes, and increased volcanic activity. The ash and chemicals raining down would cause a mass extinction on Earth.

But after a few weeks, things would start to settle.

Luna would adjust to its new position between the Earth and the Moon. The pull from both bodies would cause land tides and volcanic activity on the new moon; it would develop activity akin to Jupiter’s volcanic moon Io. The constant volcanic activity would make Luna smooth and uniform, as well as a beautiful fixture in the night sky.

New Horizons captured this image of volcanic activity on Io. The same sight could be seen of Luna from Earth. Image credit: NASA/courtesy of nasaimages.org

The Earth would also adjust to its two moons, giving life a chance to arise. But life on a two-mooned Earth would be different.

The combined light from the Moon and Luna would make for much brighter nights, and their different orbital periods will mean the Earth would have fewer fully dark nights. This will lead to different kinds of nocturnal beings; nighttime hunters would have an easier time seeing their prey, but the prey would develop better camouflage mechanisms. The need to survive could lead to more cunning and intelligent breeds of nocturnal animals.

Humans would have to adapt to the challenges of this two-mooned Earth. The higher tides created by Luna would make shoreline living almost impossible — the difference between high and low tides would be measured in thousands of feet. Proximity to the water is a necessity for sewage draining and transport of goods, but with higher tides and stronger erosion, humans would have to develop different ways of using the oceans for transfer and travel. The habitable area of Earth, then, would be much smaller.

The measurement of time would also be different. Our months would be irrelevant. Instead, a system of full and partials months would be necessary to account for the movement of two moons.

A scale comparison of the Earth, the Moon, and Jupiter’s largest moons (the Jovian moons). Image credit:Image Credit: NASA/courtesy of nasaimages.org

Eventually, the Moon and Luna would collide; like the Moon is now, both moons would be receding from Earth. Their eventual collision would send debris raining through Earth’s atmosphere and lead to another mass extinction. The end result would be one moon orbiting the Earth, and life another era of life would be primed to start.

Source: Neil Comins’ What if the Earth had Two Moons? And Nine Other Thought Provoking Speculations on the Solar System.

Posted on by David Warmflash

Phobos-Grunt Predicted to Fall in Afghanistan on January 14

Engineers tuck Phobos-Grunt into the rocket fairing. Credit: Roscosmos

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According to a news report in RiaNovosti, Russia’s Phobos-Grunt spacecraft will fall January 14th, “somewhere between 30.7 degrees north and 62.3 degrees east,” placing debris near the city of Mirabad, in southwestern Afghanistan. RiaNovosti said this prediction is according to the United States Strategic Command who calculated the craft will reenter Earth’s atmosphere at 2:22 am.

Editor’s Update: In a call to USSTRATCOM to verify this information, a spokesperson said, “We are not making any statement at USSTRACOM at this time because we are not the lead for this event and cannot make an official statement for any predictions or what is releasable at this time.”

“Please note that the U.S. Strategic Command prediction had a large uncertainty associated with it, i.e., 11 days,” Nicholas L. Johnson, NASA’s Chief Scientist for Orbital Debris told Universe Today in an email. “No one is yet able to predict with confidence the day the Phobos-Grunt will reenter.”


If the probe is predicted to fall on land, this raises the possibility of recovering the Planetary Society’s Living Interplanetary Flight Experiment (LIFE), designed to investigate how life forms could spread between neighboring planets.

The Phobos-Grunt mission profile. Credit: Roscosmos

Carrying about 50 kilograms of scientific equipment, the unpiloted Phobos-Grunt probe was launched November 9th on a mission to the larger of Mars two small moons. Although the Zenit 2 rocket that launched the craft functioned flawlessly, sending Grunt into a low Earth orbit, the upper stage booster, known as Fregat, failed to boost the orbit and send it on a trajectory toward Mars. Thought to have reverted to safe mode, Phobos-Grunt has been flying straight and periodically adjusting her orbit using small thruster engines. While this maneuvering has extended the amount of time that the probe could remain in space before reentering Earth’s atmosphere, ground controllers have been struggling to establish a communication link.

For a while, space commentators considered the possibility that Grunt might be sent on an alternate mission to Earth’s Moon or an asteroid, if control could be restored after the window for a launch to Mars and Phobos was lost. During the past few weeks, the European Space Agency (ESA) started and ended efforts to communicate with the spacecraft on several occasions, but succeeded only twice. Various scenarios were imagined in which aspects of the probe’s mission could be salvaged, despite the serious malfunction that prevented the craft from leaving Earth orbit. But at this point, the only direction for the spacecraft to go is down.

In addition to equipment for making celestial and geophysical measurements and for conduct mineralogical and chemical analysis of the Phobosian regolith (crushed rock and dust), Grunt carries Yinhou-1, a Chinese probe that was to orbit Mars for two years. After releasing Yinhou-1 into Mars orbit and landing on Phobos, Grunt would have launched a return capsule, carrying a 200 gram sample of regolith back to Earth. Also traveling within the return capsule is the Planetary Society’s Living Interplanetary Flight Experiment (LIFE).

The Planetary Society’s Living Interplanetary Flight Experiment (LIFE) capsule, on board the Phobos-Grunt spacecraft. Credit:The Planetary Society

Specifically, LIFE is designed to study the effects of the interplanetary environment on various organisms during a long duration flight in space beyond the Van Allen Radiation Belts, which protect organisms in low Earth orbit from some of the most powerful components of space radiation. Although the spacecraft has not traveled outside of the belts, the organisms contained within the LIFE biomodule will have been in space for more than two months when the probe reenters the atmosphere.

The many tons of toxic fuel are expected to explode high in the atmosphere. However, since the return capsule is designed to survive the heat of reentry and make a survivable trajectory to the ground, it is quite possible that it will reach Afghanistan in one piece. Because the LIFE biomodule is designed to withstand an impact force of 4,000 Gs, it is possible that the experiment can be recovered and the biological samples studied.

To be sure, the possibility of recovering an unharmed returned capsule and LIFE depends on the willingness of the inhabitants around the landing site to allow the Russian Space Agency to pick it up. Given the proximity of the predicted landing area to a war zone and the fact that the Taliban are not known for being enthusiastic about space exploration and astrobiology, it is also possible that a landing on land could turn out no better than a landing over the deepest part of the ocean.

Source: RiaNovosti

Posted on by Paul Scott Anderson

New Study Says Large Regions of Mars Could Sustain Life

The Planet Mars. Image credit: NASA
The Planet Mars. Image credit: NASA

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The question of whether present-day Mars could be habitable, and to what extent, has been the focus of long-running and intense debates. The surface, comparable to the dry valleys of Antarctica and the Atacama desert on Earth, is harsh, with well-below freezing temperatures most of the time (at an average of minus 63 degrees Celsius or minus 81 Fahrenheit), extreme dryness and a very thin atmosphere offering little protection from the Sun’s ultraviolet radiation. Most scientists would agree that the best place that any organisms could hope to survive and flourish would be underground. Now, a new study says that scenario is not only correct, but that large regions of Mars’ subsurface could be even more sustainable for life than previously thought.

Scientists from the Australian National University modeled conditions on Mars on a global scale and found that large regions could be capable of sustaining life – three percent of the planet actually, albeit mostly underground. By comparison, just one percent of Earth’s volume, from the central core to the upper atmosphere, is inhabited by some kind of life. They compared pressure and temperature conditions on Earth to those of Mars to come up with the surprising results.

According to Charley Lineweaver of ANU, “What we tried to do, simply, was take almost all of the information we could and put it together and say ‘is the big picture consistent with there being life on Mars?’ And the simple answer is yes… There are large regions of Mars that are compatible with terrestrial life.”

So it seems that while, as we know, the surface of Mars is quite inhospitable to most forms of life (that we know of) except perhaps for some extremophiles, conditions underground are a different matter. It is already known that there are vast deposits of ice below the surface even near the equator (as well as the polar ice caps of course), so there could be liquid water a bit deeper where it is warmer. Those conditions would be ideal for bacteria or other simple organisms. While that idea has been proposed and discussed before, Lineweaver’s findings support it on a planet-wide basis – previous studies tended to focus on specific locations in a “piecemeal” approach, but these new ones take the entire planet into consideration.

The paper is currently available for free here. Abstract:

We present a comprehensive model of martian pressure-temperature (P-T) phase space and compare it with that of Earth. Martian P-T conditions compatible with liquid water extend to a depth of *310 km. We use our phase space model of Mars and of terrestrial life to estimate the depths and extent of the water on Mars that is habitable for terrestrial life. We find an extensive overlap between inhabited terrestrial phase space and martian phase space. The lower martian surface temperatures and shallower martian geotherm suggest that, if there is a hot deep biosphere on Mars, it could extend 7 times deeper than the *5km depth of the hot deep terrestrial biosphere in the crust inhabited by hyperthermophilic chemolithotrophs. This corresponds to *3.2% of the volume of present-day Mars being potentially habitable for terrestrial-like life. Key Words: Biosphere—Mars— Limits of life—Extremophiles—Water. Astrobiology 11, xxx–xxx.

Posted on by Paul Scott Anderson

The Habitable Exoplanets Catalog is Now Online!

Credit: The Habitable Exoplanets Catalog, Planetary Habitability Laboratory @ UPR Arecibo (phl.upl.edu)

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Anyone who has an interest in exoplanets probably knows about the various online catalogs that have become available in recent years, such as The Extrasolar Planets Encyclopaedia for example, providing up-to-date information and statistics on the rapidly growing number of worlds being discovered orbiting other stars. So far, these have been listings of all known exoplanets, both candidates and confirmed. But now there is a new catalog published by the Planetary Habitability Laboratory (a project of the University of Puerto Rico at Arecibo), which focuses exclusively on those planets which have been determined to be potentially habitable. The Habitable Exoplanets Catalog is a database which will serve as a key resource for scientists and educators as well as the general public.

As of right now, there are two confirmed planets and fourteen candidates listed, but those numbers are expected to grow over the coming months and years as more candidates are found and more of those candidates are confirmed. There is even a listing of habitable moons, whose existence have been inferred from the data, although none have been observed yet (finding exoplanets is challenging enough, but exomoons even more so!).

According to Abel Méndez, Director of the PHL and principal investigator, “One important outcome of these rankings is the ability to compare exoplanets from best to worst candidates for life.” He adds: “New observations with ground and orbital observatories will discover thousands of exoplanets in the coming years. We expect that the analyses contained in our catalog will help to identify, organize, and compare the life potential of these discoveries.”

The big question of course is whether any habitable planets are actually inhabited, two different things. To help answer that, it will be necessary to further analyze the atmospheres and surfaces of those planets, looking for any indication of possible biosignatures such as oxygen or methane. Kepler can’t do that directly, but subsequent telescopes such as the Terrestrial Planet Finder (TPF) will be able to, and provide a more accurate assessment of their physical composition, climate, etc.

Not long ago it wasn’t known if there even were any planets orbiting other stars; now we’re finding them by the thousands and soon we’ll be able to distinguish their unique physical characteristics and have a better idea of how many habitable worlds are out there – exciting times.

Posted on by Paul Scott Anderson

Kepler Confirms First Planet in Habitable Zone of Sun-Like Star

This artist's illustration of Kepler 22-b, an Earth-like planet in the habitable zone of a Sun-like star about 640 light years (166 parsecs) away. Credit: NASA/Ames/JPL-Caltech

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Scientists from the Kepler mission announced this morning the first confirmed exoplanet orbiting in the habitable zone of a Sun-like star, the region where liquid water could exist on the surface of a rocky planet like Earth. Evidence for others has already been found by Kepler, but this is the first confirmation. The planet, Kepler-22b, is also only about 2.4 times the radius of Earth — the smallest planet found in a habitable zone so far — and orbits its star, Kepler-22, in 290 days. It is about 600 light-years away from Earth, and Kepler-22 is only slightly smaller and cooler than our own Sun. Not only is the planet in the habitable zone, but astronomers have determined its surface temperature averages a comfortable 22 degrees C (72 degrees F). Since the planet’s mass is not yet known, astronomers haven’t determined if it is a rocky or gaseous planet. But this discovery is a major step toward finding Earth-like worlds around other stars. A very exciting discovery, but there’s more…

It was also announced that Kepler has found 1,094 more planetary candidates, increasing the number now to 2,326! That’s an increase of 89% since the last update this past February. Of these, 207 are near Earth size, 680 are super-Earth size, 1,181 are Neptune size, 203 are Jupiter size and 55 are larger than Jupiter. These findings continue the observational trend seen before, where smaller planets are apparently more numerous than larger gas giant planets. The number of Earth size candidates has increased by more than 200 percent and the number of super-Earth size candidates has increased by 140 percent.

According to Natalie Batalha, Kepler deputy science team lead at San Jose State University in San Jose, California, “The tremendous growth in the number of Earth-size candidates tells us that we’re honing in on the planets Kepler was designed to detect: those that are not only Earth-size, but also are potentially habitable. The more data we collect, the keener our eye for finding the smallest planets out at longer orbital periods.”

Regarding Kepler-22b, William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, California stated: “Fortune smiled upon us with the detection of this planet. The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season.”

Comparison of the Kepler-22 system with our own inner solar system. Credit: NASA/Ames/JPL-Caltech

Previously there were 54 planetary candidates in habitable zones, but this was changed to 48, after the Kepler team redefined the definition of what constitutes a habitable zone in order to account for the warming effects of atmospheres which could shift the zone farther out from a star.

The announcements were made at the inaugural Kepler science conference which runs from December 5-9 at Ames Research Center.

See also the press release from the Carnegie Institution for Science here.

Posted on by Bruce Dorminey

Why Silicon-based Aliens Would Rather Eat our Cities than Us: Thoughts on Non-carbon Astrobiology

A graphic associated with the original 'War of the Worlds' by H.G. Wells.

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Editor’s note: Bruce Dorminey, science journalist and author of “Distant Wanderers: The Search for Planets Beyond the Solar System,” interviews NASA astrochemist Max Bernstein for Universe Today about the possibility of Silicon-based life.

Conventional wisdom has long had it that carbon-based life, so common here on earth, must surely be abundant elsewhere; both in our galaxy and the universe as a whole.

This line of reasoning is founded on two major assumptions; the first being that complex carbon chain molecules, the building blocks of life as we know it, have been detected throughout the interstellar medium.  Carbon’s abundance appears to stretch across much of cosmic time, since its production is thought to have peaked some 7 billion years ago, when the universe was roughly half its current age.

The other major assumption is that life needs an elixir, a solvent on which it can advance its unique complex chemistry.  Water and carbon go hand in hand in making this happen.

While the world as we know it runs on carbon, science fiction’s long flirtation with silicon-based life — “It’s life, but not as we know it” — has become a familiar catchphrase.  But life of any sort should evolve, eat, excrete, reproduce, and respond to stimulus.

And although non-carbon based life is a very long shot, we thought we’d broach the issue  with one of the country’s top astrochemists — Max Bernstein, the Research Lead of the Science Mission Directorate at NASA headquarters in Washington,D.C.

Bruce Dorminey — IS IT WRONG TO ASSUME THAT LIFE COULD BE BASED ON SOMETHING OTHER THAN CARBON?

Max Bernstein. Credit: NASA

Max Bernstein — It’s important for us to keep an open mind about alien life, lest we come across it and miss it. On the other hand, carbon is much better than any other element in forming the main structures of living things.  Carbon can form many stable complex structures of great diversity. When carbon forms molecules containing cxygen and nitrogen, the carbon bonds to nitrogen and oxygen are stable.  But not so much so that they can’t be fairly easily undone, unlike silicon-oxygen bonds, for example.

Dorminey — DOES THE RECENT NASA-FUNDED RESEARCH AT MONO LAKE, CALIFORNIA WHICH TOUTED THE DISCOVERY OF BACTERIA WITH DNA THAT USES ARSENIC INSTEAD OF PHOSPHORUS RATTLE THE CURRENT PARADIGM?

Bernstein — That was a really cool result, but the basic structure was still carbon. The arsenic was said to have replaced phosphorus, not carbon.  The discovery of this putative arsenic organism may prove to be incorrect, but it’s a hypothesis with science behind it, and not just someone tossing out an idea and leaving it at the level of what if you replaced carbon with silicon?

The structure of silane, the silicon-based analogue of methane.

Dorminey — SILICON SEEMS TO BE THE MOST POPULAR NON-CARBON BASED CANDIDATE, ARE THERE OTHERS THAT ALSO MIGHT BE FEASIBLE?

Bernstein — It’s hard to imagine anything that would be more likely that silicon because there is nothing closer to carbon than silicon in terms of its chemistry. It’s in the right place on the periodic table, just below carbon.  On the face of it, [silicon-based life] doesn’t seem too absurd since silicon, like carbon, forms four bonds. CH4 is methane and SiH4 is silane.  They are analogous molecules so the basic idea is that perhaps silicon could form an entire parallel chemistry, and even life.  But there are tons of problems with this idea.   We don’t see a complex stable chemistry [solely] of silicon and hydrogen, as we see with carbon and hydrogen.  We use hydrocarbon chains in our lipids (molecules that make up membranes), but the analogous silane chains would not be stable.  Whereas carbon-oxygen bonds can be made and unmade — this goes on in our bodies all the time — this is not true for silicon.  This would severely limit silicon’s life-like chemistry.  Maybe you could have something silicon-based that’s sort of alive, but only in the sense that it passes on information.

Dorminey — IF SILICON-BASED LIFE IS OUT THERE, HOW COULD WE EVER DETECT IT REMOTELY?

Bernstein — We are seriously arguing about how we would remotely detect life just like us, so I really couldn’t say.  Presumably technology-using organisms, whatever their biochemistry, will produce technology, so the Search for Extraterrestrial Intelligence (SETI) may be our best shot.

Dorminey— HOW WOULD YOU LOOK FOR SILICON-BASED LIFE HERE ON EARTH?

Bernstein — When seeking an alien organism its really tough because you just don’t know what molecules to look for.  One would have to be satisfied by something a bit more ambiguous, like sets of molecules that should not be there. For example, if you were an alien Silicon organism, you might not be looking for our biochemistry, but the fact that you kept seeing exactly the same chain lengths over and over again might tip you off to the fact that those darn carbon chains might actually be the basis of an organism’s membranes.

A Horta, a fictional silicon-based life-form in the Star Trek universe. Image from Star Trek: The Original Series © 1967 Paramount Pictures

Dorminey — WHERE ARE THE LARGEST CONCENTRATIONS OF SILICON HERE?
IN SAND?

Bernstein — In sand or rock. There are literally megatons of silicate minerals on Earth.

Dorminey — HAS ANYONE EVER CLAIMED DETECTION OF SELF-REPLICATING EXAMPLES OF SILICON HERE ON EARTH?

Bernstein — There have been ideas about minerals holding information just as DNA holds information.  DNA holds information in a chain that is read from one end to the other.  In contrast, a mineral could hold information in two dimensions [on its surface].  A crystal grows when new atoms arrive on the surface, building layer upon layer.  So, if a crystal sheet cleaved off and then started to grow that would be like the birth of a new organism and would carry information from generation to generation.  But is a replicating crystal alive?  To date, I don’t think that there is actually any evidence that minerals pass information like this.

Dorminey — IS THE CRUX OF THE PROBLEM THAT SILICON-BASED LIFE WOULD BE SO SLOWLY REPLICATING THAT IT COULD NEVER MAKE IT IN A DYNAMIC UNIVERSE?

Bernstein — I don’t think that any Silicon life form could be a biological threat to us.  If they were high tech, they might eat our buildings or shoot guns at us but I don’t see how they could infect us.  We run hot and move fast.  If we don’t, things will catch us and eat us.

If they are also tougher than we are and whatever feeds on them is also slow and Silicon based maybe being slow doesn’t matter.

Dorminey — WHAT WOULD BE THE SIGNATURES OF SILICON-BASED LIFE?

Bernstein — If they are not technological, they would be very tough to detect.  We could look for unstable, unexpected silicon molecules; some high energy molecule that should not be there, or molecular chains of all the same length.

Dorminey — DO YOU THINK THAT SILICON-BASED LIFE MIGHT EXIST SOMEWHERE OUT THERE?

Bernstein — Maybe deep below the surface of a planet in some very hot hydrogen-rich, Oxygen-poor environment, you would have this complex silane chemistry.  There, maybe silanes would form reversible silicon bonds with selenium or tellurium.

Dorminey — IF SUCH SILICON-BASED LIFE DID CROP UP, WHAT WOULD BE ITS EVOLUTIONARY ENDGAME?

Bernstein — If it could evolve past the protist [microorganism] stage, then I think it could evolve intelligence.  I have no idea how likely it is for intelligence to evolve, but I can believe in silicon crystals passing information from layer to layer or in silicon artificial intelligence, but I don’t expect to see silicon apes playing their equivalent of “Angry Birds” on their Silicon-Phones.

Dorminey — IF SILICON-LIFE DID EVOLVE, WOULD ITS LIFESPAN BE MUCH LONGER THAN ITS CARBON-BASED ANALOGUES?

Bernstein — The replicating mineral that I described earlier would be living very, very slowly on Earth’s surface.  But maybe somewhere very much hotter, its lifespan would be shorter.  That’s because presumably lifespan is connected to the pace of your chemistry, which depends on temperature.

Dorminey — FINALLY, WHAT WOULD ENDANGER NON-CARBON-BASED LIFE?

Bernstein — Physical harm for sure.  Presumably you could take a jackhammer to it?

But our biochemistry would not be pathogens to it; we could not “infect” them as was the case in “War of the Worlds.”

Posted on by Paul Scott Anderson

Could Curiosity Determine if Viking Found Life on Mars?

The landing site of Viking 1 on Mars in 1977, with trenches dug in the soil for the biology experiments. Credit: NASA/JPL

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One of the most controversial and long-debated aspects of Mars exploration has been the results of the Viking landers’ life-detection experiments back in the 1970s. While the preliminary findings were consistent with the presence of bacteria (or something similar) in the soil samples, the lack of organics found by other instruments forced most scientists to conclude that the life-like responses were most likely the result of unknown chemical reactions, not life. Gilbert V. Levin, however, one of the primary scientists involved with the Viking experiments, has continued to maintain that the Viking landers did indeed find life in the Martian soil. He also now thinks that the just-launched Curiosity rover might be able to confirm this when it lands on Mars next summer.

Curiosity is not specifically a life-detection mission. Rather, it continues the search for evidence of habitability, both now and in the past. But is it possible that it could find evidence for life anyway? Levin believes it could, between its organics detection capability and its high-resolution cameras.

The major argument against the life-detection claims was the lack of organics found in the soil. How could there be life with no organic building blocks? It has since been thought that any organics were destroyed by the harsh ultraviolet radiation or other chemical compounds in the soil itself. Perchlorates could do that, and were later found in the soil by the Phoenix mission a few years ago, closer to the north pole of Mars. The experiments themselves, which included baking the soil at high heat, may have destroyed any organics present (part of the studies involved heating the soil to kill any organisms and then study the residual gases released as a result, as well as feeding nutrients to any putative organisms and analyzing the gases released from the soil). If Curiosity can find organics, either in the soil or by drilling into rocks, Levin argues, that would bolster the case for life being found in the original Viking experiments, as they were the “missing piece” to the puzzle.

So what about the cameras? Any life would have to be macro, of visible size, to be detected. Levin and his team had also found “greenish coloured patches” on some of the nearby rocks. (I still have a little booklet published by Levin at the time, “Color and Feature Changes at Mars Viking Lander Site” which describes these in more detail). When as a test, lichen-bearing rocks on Earth were viewed with the same camera system using visible and infrared spectral analysis, the results were remarkably similar to what was seen on Mars. Again, since then though, those results have been widely disputed, with most scientists thinking the patches were mineral coatings similar to others seen since then. Of course, there is also the microscopic imager, similar to that on the Spirit and Opportunity rovers, although microorganisms would still be too small to be seen directly.

Regardless, Levin feels that Curiosity just might be able to vindicate his earlier findings, stating “This is a very exciting time, something for which I have been waiting for years. At the very least, the Curiosity results may bring about my long-requested re-evaluation of the Viking LR results. The Viking LR life detection data are the only data that will ever be available from a pristine Mars. They are priceless, and should be thoroughly studied.”