View of Mars from Viking 2 lander, September 1976. (NASA/JPL-Caltech)
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The Curiosity rover is currently on its way to Mars, scheduled to make a dramatic landing within Gale Crater in mid-August and begin its hunt for the geologic signatures of a watery, life-friendly past. Solid evidence that large volumes of water existed on Mars at some point would be a major step forward in the search for life on the Red Planet.
But… has it already been found? Some scientists say yes.
Researchers from universities in Los Angeles, California, Tempe, Arizona and Siena, Italy have published a paper in the International Journal of Aeronautical and Space Sciences (IJASS) citing the results of their work with data obtained by NASA’s Viking mission.
The twin Viking 1 and 2 landers launched in August and September of 1975 and successfully landed on Mars in July and September of the following year. Their principal mission was to search for life, which they did by digging into the ruddy Martian soil looking for signs of respiration — a signal of biological activity.
A six-inch-deep trench in the Martian soil dug by Viking 1 in February 1977. The goal was to reach a foot below the surface for sampling.
The results, although promising, were inconclusive.
Now, 35 years later, one team of researchers claims that the Viking landers did indeed detect life, and the data’s been there all along.
“Active soils exhibited rapid, substantial gas release,” the team’s report states. “The gas was probably CO2 and, possibly, other radiocarbon-containing gases.”
By applying mathematical complexities to the Viking data for deeper analysis, the researchers found that the Martian samples behaved differently than a non-biological control group.
“Control responses that exhibit relatively low initial order rapidly devolve into near-random noise, while the active experiments exhibit higher initial order which decays only slowly,” the paper states. “This suggests a robust biological response.”
While some critics of the findings claim that such a process of identifying life has not yet been perfected — not even here on Earth — the results are certainly intriguing… enough to bolster support for further investigation into Viking data and perhaps re-evaluate the historic mission’s “inconclusive” findings.
Artist concept of an exoplanet. Credit: David A. Hardy.
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According to Star Trek lore, it is only 51 years until humans encounter their first contact with an alien species. In the movie “Star Trek: First Contact,” on April 5, 2063, Vulcans pay a visit to an Earth recovering from a war-torn period (see the movie clip below.) But will such a planet-wide, history-changing event ever really take place? If you are logical, like Spock and his Vulcan species, science points towards the inevitability of first contact. This is according to journalist Marc Kaufman, who is a science writer for the Washington Post and author of the book “First Contact: Scientific Breakthroughs in the Hunt for life Beyond Earth.” He writes that from humanity’s point of view, first contact would be a “harbinger of a new frontier in a dramatically changed cosmos.”
What are some of the arguments for and against the likelihood of first contact ever taking place and what would the implications be?
“One argument against first contact is from those who say there is no other life in the Universe,” said Kaufman, speaking to Universe Today via phone, “and with that is the Fermi paradox, which says that if there is so much life out there, why hasn’t it visited us yet? That was first posited back in the 1950’s and with everything we’ve learned since then, it seems rather presumptuous and Earth-centric to say that because no one has come to Earth, there is no life out there.”
Kaufman argues the Universe is so vast, the number of exoplanets is so huge – with the number of exoplanets in habitable zones now gaining in numbers almost daily – and we now understand that all the makings for the building blocks of life are out in space, so it defies logic to argue there is no other life out there.
Another argument against first contact states there might be microbial life elsewhere in the Universe, but it is not intelligent. “This is where the Fermi paradox comes in even more,” Kaufman said. “It certainly is true — as far as we know — that no intelligent life has made contact with Earth. But when you look at the amount of time we’ve been a technologically advanced society, it has only been a few hundred years. In the vastness of time, that is a pitifully small amount of time – truly nothing.”
In the immensity of cosmological time, Kaufman said, it is quite possible that microbial life emerged and evolved a billion years ago on another world and we missed coinciding with it, as civilizations could have come and gone.
“But all the makings are there and unless we want to say that Earth was made through divine creation or only through an unbelievable set of circumstances this is the only place in the Universe where life began, it just seems hugely, hugely implausible,” Kaufman said.
So, Kaufman says, the best, most logical argument is that life exists beyond Earth and in some instances includes what we would consider intelligence.
“If you have microbial life and billions of planets in habitable zones, the logic says that some of them will advance like we did,” Kaufman said. “There’s no reason to say that evolution is exclusive to Earth. It feels very 14th or 15th century-Earth-centric to say that we are the only place where there is intelligent life.”
Our continued scientific understanding, and in particular, the recent ongoing finding of so many exoplanets, has been a real revolution in our understanding of the cosmos, Kaufman said, and it is a huge boost to the logic of finding life elsewhere.
“It was hypothesized for decades, if not centuries that other planets were out there,” he said. “Now that we are finding planets almost every day, from a scientific perspective, it shows us that if the science is pointing in a certain direction, you just need to have the technology and the knowledge catch up to that hypothesis.”
Kaufman says that like the surge in finding exoplanets, astrobiology is likely the next area of science where breakthroughs will happen.
“Scientists almost unanimously believe there is other life out there, but we just don’t have the technology to find it yet,” he said. “Even with the recent potential cuts in NASA’s budget for planetary missions, and even if NASA is not able to send up as many missions, there is a broad movement going on in college campuses and institutes – from working on synthetic life, to studies in cosmology, and astrochemistry — all of those things are moving forward because there is a real sense that something is within reach. This area of science is just going to blossom.”
So if tomorrow (or on April 5, 2063) a spaceship shows up, how would we respond?
“On one level, I’d hope there would be a huge amount of wonder and awe and a recognition of the vastness of the Universe. But I also imagine there would be a lot of defensiveness, as well,” said Kaufman, referring to some, like Stephen Hawking, who say we shouldn’t send messages out into space — because if a more technically advanced civilization comes to Earth, the outcome for the less advanced (us) would likely be bad.
But Kaufman has hope that Earthlings would welcome a visit.
“Look at the continuing fascination of Roswell or UFOs,” he said. “Throughout history, humans have looked to the skies and thought that we’ve experienced something ‘out there’ – be it angels or gods or spaceships. There is, I believe, a deep human craving that we aren’t alone, and that would be a significant part of our response.”
For more information see Kaufman’s book, and website,”Habitable Zones”
Extreme heating from tidal stresses may render a "Tidal Venus" planet inhabitable
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Earth-sized exoplanets within a distant star’s habitable zone could still be very much uninhabitable, depending on potential tidal stresses — either past or present — that could have “squeezed out” all the water, leaving behind a bone-dry ball of rock.
New research by an international team of scientists suggests that even a moderately eccentric orbit within a star’s habitable zone could exert tidal stress on an Earth-sized planet, enough that the increased surface heating due to friction would boil off any liquid water via extreme greenhouse effect.
Such planets are dubbed “Tidal Venuses”, due to their resemblance to our own super-heated planetary neighbor. This evolutionary possibility could be a factor in determining the actual habitability of an exoplanet, regardless of how much solar heating (insolation) it receives from its star.
The research, led by Dr. Rory Barnes of the University of Washington in Seattle, states that even an exoplanet currently in a circular, stable orbit could have formed with a much more eccentric orbit, thus subjecting it to tidal forces. Any liquid water present after formation would then have been slowly but steadily evaporated and the necessary hydrogen atoms lost to space.
The risk of such a “desiccating greenhouse” effect would be much greater on exoplanets orbiting lower-luminosity stars, since any potential habitable zone would be closer in to the star and thus prone to stronger tidal forces.
And as far as such an effect working to create habitable zones further out in orbit than otherwise permissible by stellar radiation alone… well, that wouldn’t necessarily be the case.
Even if an exoplanetary version of, say, Europa, could be heated through tidal forces to maintain liquid water on or below its surface, a rocky world the size of Earth (or larger) would still likely end up being rather inhospitable.
“One couldn’t do it for an Earthlike planet — the tidal heating of the interior would likely make the surface covered by super-volcanoes,” Dr. Barnes told Universe Today.
So even though the right-sized exoplanets may be found in the so-called “Goldilocks zone” of their star, they may still not be “just right” for life as we know it.
Map of 226 ancient lakes on Mars. Credit: Goudge, T.A., Head, J.W., Mustard, J.F. and Fassett, C.I./MOLA/NASA
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Mars was once a much wetter world than it is now, with hot springs, rivers, lakes and perhaps even oceans. Just how wet exactly, and for how long, is still a subject of considerable debate. One vital clue comes from clay mineral deposits and sediments left over after the water disappeared, but still visible now. They provide a valuable insight into what Mars used to be like, and why it is the cold, dry place we see today.
A team of scientists from Brown University has just completed a new study of ancient lake beds on Mars, specifically looking at the clay deposits within them, to try to determine how many of these lakes still contain such deposits and their composition. So what do they tell us about conditions on early Mars? How does this affect the search for evidence of life?
As it turns out, about a third of the lake beds examined still show evidence for clay deposits. A total of 79 lake beds out of 226 studied to be exact, indicating that they are less common on Mars than on Earth. The reason for this may be that the chemistry of the water was not ideal for preserving clays or that the lakes were relatively short-lived.
The paper was just published in Icarus on March 2, 2012.
From the abstract:
“These results indicate that hydrated and evaporite minerals are not as commonly associated with lacustrine deposits on Mars as they are on Earth. This suggests in situ alteration and mineral precipitation, a common source of such minerals in terrestrial lakes, was not a major process occurring in these paleolacustrine systems, and that the observed minerals are likely to be present as transported material within the lacustrine deposits. The lack of widespread in situ alteration also suggests that either the water chemistry in these paleolake systems was not conducive to aqueous alteration and mineral precipitation, or that the open-basin lake systems were relatively short-lived.”
Images for the study came from the Mars Reconnaissance Orbiter, Mars Odyssey and Mars Express spacecraft.
Clay deposits have become a primary focus of study by orbiters and rovers, as they could preserve fossil traces of early life, just as they do on Earth. Even if they are less common on Mars, the fact that they do exist there is exciting, and there is now much interest in exploring them further. Apart from underground, they are the best places to look for such evidence of life. It is also possible that additional deposits have been buried underground, waiting to be discovered.
The Opportunity rover is currently very close to a treasure trove of clays in Endeavour crater, and it is expected to head straight for them after its winter “hibernation” is over in the next few months. The Curiosity rover, en route to Mars right now, will land in Gale crater next July, where there are also clay deposits near the base of a mountainous peak within the crater. Gale crater is thought to be another site of a former Martian lake.
The abstract is available here (with full paper available for purchase).
Along with Jupiter’s moon Europa, a tiny Saturnian moon, Enceladus, has become one of the most fascinating places in the solar system and a prime target in the search for extraterrestrial life. Its outward appearance is that of a small, frozen orb, but it revealed some surprises when the Cassini spacecraft gave us our first ever close-up look at this little world – huge geysers of water vapour spewing from its south pole. The implications were thought-provoking: Enceladus, like Europa, may have an ocean of liquid water below the surface. Unlike Europa however, the water is apparently able to make it up to the surface via fissures, erupting out into space as giant plumes.
Now, a new project sponsored by the German Aerospace Center, Enceladus Explorer, was launched on February 22, 2012, in an attempt to answer the question of whether there could be life on (or rather, inside) Enceladus. The project lays the groundwork for a new, ambitious mission being proposed for some time in the future.
Cassini was able to sample some of the plumes directly during its closest approaches to the moon, revealing that they contain water vapour, ice particles and organic molecules. If they originate from a reservoir of subsurface liquid water, as now thought by most scientists involved, it would indicate an environment which could be ideal for life to have started. The necessary ingredients for life (as we know it at least) are all there – water, heat and organic material. The fissures themselves generate much more heat relatively than the surrounding surface, suggesting that the conditions below the surface are much warmer. Maybe not “hot” per se, but warm enough, perhaps also with the aid of salts like in Earth’s oceans, to keep the water liquid.
But what is the best way to search for evidence of life there? Follow-up missions have been proposed, to again sample the plumes, but with instruments able to look for life itself, which Cassini can’t do. This would seem ideal, as the water is being spewed out into space, with no drilling through the ice necessary. But the Enceladus Explorer project is proposing to do just that; the rationale is that any organisms (most likely microscopic) which may be in the water could easily be destroyed by the force of the ejection from the fissure. So then what is the best way to sample the water itself down below?
Enceladus Explorer would place a base station on the surface near one of the fissures; an ice drilling probe, the IceMole, would then melt its way through the ice crust to a depth of 100-200 metres until it reaches a liquid water reservoir. It would obtain samples of the water and examine them in situ for any traces of microorganisms. With no GPS system available, or external reference points to use, the probe would need to function autonomously, finding its own way through the ice to the water below.
The IceMole is already being tested here on Earth, and has successfully melted its way through the ice of the Morteratsch glacier in Switzerland. The next experiment will have it navigate its way through ice in the Antarctic, sampling completely uncontaminated water from a subsurface lake below the ice, much like the conditions found on Enceladus.
There is no timeframe yet for such a mission, especially given current budgets, but the Enceladus Explorer project has already shown that it is certainly technologically feasible and would provide an incredible look at an environment in the outer solar system which is amazingly Earth-like yet utterly alien at the same time.
Earth’s next Mars rover will NOT be made in USA. President Obama has killed NASA funding for the ExoMars Rover joint project by NASA and ESA planned for 2018 Launch and designed to search for evidence of life. Credit: ESA - Annotation: Ken Kremer
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Earth’s next Mars Rover – NOT Made in USA
Just days after President Obama met with brilliant High School students at the 2012 White House Science Fair to celebrate their winning achievements and encourage America’s Youth to study science and take up careers in the Science, Technology, Engineering and Math (STEM) technical fields, the Obama Administration has decided on deep budgets cuts slashing away the very NASA science programs that would inspire those same students to shoot for the Stars and Beyond and answer the question – Are We Alone ?
Last year, the Obama Administration killed Project Constellation, NASA’s Human Spaceflight program to return American astronauts to the Moon. This year, the President has killed NASA’s ExoMars Robotic Spaceflight program aimed at dispatching two ambitious missions to Mars in 2016 and 2018 to search for signs of life.
Both ExoMars probes involved a joint new collaboration with the European Space Agency (ESA) carefully crafted to share costs in hard times and get the most bang for the buck – outlined in my earlier Universe Today story, here.
Expert Scientists and Policy makers have been voicing their opinions.
President Obama meets America’s brightest Young Rocket Scientists
President Barack Obama hosted the winning science fair students from a range of nationwide competitions at the 2nd White House Science Fair on February 7, 2012. The ExoMars missions were eliminated from the NASA budget announced on Feb. 13, 2012.
All of NASA’s “Flagship” Planetary Science missions have now been cancelled in the 2013 Fiscal Year Budget proposed on Feb. 13, and others missions have also been curtailed due to the severe economy.
“There is no room in the current budget proposal from the President for new Flagship missions anywhere,” said John Grunsfeld, NASA’s Associate Administrator for Science at a NASA budget briefing for the media on Feb. 13.
ESA is now looking to partner with Russia as all American participation in ExoMars is erased due to NASA’ s forced pull out.
On Feb. 13, NASA’s Fiscal 2013 Budget was announced and the Obama Administration carved away nearly half the Mars mission budget. Altogether, funding for NASA’s Mars and Planetary missions in the Fiscal 2013 budget would be sliced by $300 million – from $1.5 Billion this year to $1.2 Billion in 2013. NASA was forced to gut the Mars program to pay for the cost overruns of the James Webb Space Telescope.
Mars rover scientist Prof. Jim Bell of Arizona State University and President of The Planetary Society (TPS) told Universe Today that “no one expects increases”, but cuts of this magnitude are “cause for concern”.
NASA’s robotic missions to Mars and other solar system bodies have been highly successful, resulted in fundamental scientific breakthroughs and are wildly popular with students and the general public.
“With these large proposed cuts to the NASA Mars exploration program, there will be a lot of cause for concern,” said Bell.
“The Mars program has been one of NASA’s crown jewels over the past 15 years, both in terms of science return on investment, and in terms of public excitement and engagement in NASA’s mission. It would also represent an unfortunate retreat from the kind of international collaboration in space exploration that organizations like The Planetary Society so strongly support.”
NASA Budget Cuts in Fiscal Year 2013 will force NASA to kill participation in the joint ESA/NASA collaboration to send two Astrobiology related missions to orbit and land rovers on Mars in 2016 and 2018- designed to search for evidence of Life. Credit: ESA - Annotation: Ken Kremer
Bell and other scientists feel that any cuts should be balanced among NASA programs, not aimed only at one specific area.
“Certainly no one expects increasing budgets in these austere times, and it is not useful or appropriate to get into a battle of “my science is better than your science” among the different NASA Divisions and Programs.” Bell told me.
“However, it would be unfortunate if the burden of funding cuts were to befall one of NASA’s most successful and popular programs in a disproportionate way compared to other programs. As Ben Franklin said, “We should all hang together, or surely we will all hang separately.”
Bell added that science minded organizations should work with Congress to influence the debate over the coming months.
“Of course, this would only be an initial proposal for the FY13 and beyond budget. Over the winter, spring, and summer many professional and public organizations, like TPS, will be working with Congress to advocate a balanced program of solar system exploration that focuses on the most important science goals as identified in the recent NRC Planetary Decadal Survey, as well as the most exciting and publicly compelling missions that are supported by the public–who ultimately are the ones paying for these missions.”
“Let’s hope that we can all find a productive and pragmatic way to continue to explore Mars, the outer solar system, and our Universe beyond,” Bell concluded.
“The impact of the cuts … will be to immediately terminate the Mars deal with the Europeans,” said Scott Hubbard, of Stanford University and a former NASA planetary scientist who revived the agency’s Mars exploration program after failures in 1999, to the Washington Post. “It’s a scientific tragedy and a national embarrassment.”
“I encourage whoever made this decision to ask around; everyone on Earth wants to know if there is life on other worlds,” Bill Nye, CEO of The Planetary Society, said in a statement. “When you cut NASA’s budget in this way, you’re losing sight of why we explore space in the first place.”
“There is no other country or agency that can do what NASA does—fly extraordinary flagship missions in deep space and land spacecraft on Mars.” Bill Nye said. “If this budget is allowed to stand, the United States will walk away from decades of greatness in space science and exploration. But it will lose more than that. The U.S. will lose expertise, capability, and talent. The nation will lose the ability to compete in one of the few areas in which it is still the undisputed number one.”
Ed Weiler is NASA’s recently retired science mission chief (now replaced by Grunsfeld) and negotiated the ExoMars program with ESA. Weiler actually quit NASA specifically in opposition to the Mars Program cuts ordered by the Office of Management and Budget (OMB) and had these comments for CBS News;
“To me, it’s bizarro world,” Weiler said an interview with CBS News. “Why would you do this? The President of the United States, President Obama, declared Mars to be the ultimate destination for human exploration. Obviously, before you send humans to the vicinity of Mars or even to land on Mars, you want to know as much about the planet as you possibly can. … You need a sample return mission. The president also established a space policy a few years ago which had the concept of encouraging all agencies to have more and more foreign collaboration, to share the costs and get more for the same bucks.”
“Two years ago, because of budget cuts in the Mars program, I had to appeal to Europe to merge our programs. … That process took two long years of very delicate negotiations. We thought we were following the president’s space policy exactly. Congressional reaction was very positive about our activities. You put those factors in place and you have to ask, why single out Mars? I don’t have an answer.”
Space Analysts and Political leaders also weighed in:
“The president’s budget is just a proposal,” said Howard McCurdy, a space-policy specialist at American University in Washington to the Christian Science Monitor.
The cuts “reflect the new reality” in which the economy, budget deficits, and the federal debt have elbowed their way to the top of Washington’s agenda, McCurdy adds.
“You don’t cut spending for critical scientific research endeavors that have immeasurable benefit to the nation and inspire the human spirit of exploration we all have,” said Rep. John Culberson (R-Tex.). Texas is home to NASA’s Johnson Space Center.
Rep. Adam Schiff (D-CA), who represents the district that’s home to the Jet Propulsion Laboratory (JPL), released this statement following his meeting with NASA Administrator Charles Bolden to discuss the agency’s 2013 budget proposal:
“Today I met with NASA Administrator Charles Bolden to express my dismay over widespread reports that NASA’s latest budget proposes to dramatically reduce the planetary science program, and with it, ground breaking missions to Mars and outer planetary bodies like Jupiter’s icy moon Europa, and to inform him of my vehement opposition to such a move.”
“America’s unique expertise in designing and flying deep-space missions is a priceless national asset and the Mars program, one of our nation’s scientific crown jewels, has been a spectacular success that has pushed the boundaries of human understanding and technological innovation, while also boosting American prestige worldwide and driving our children to pursue science and engineering degrees in college.
“As I told the Administrator during our meeting, I oppose these ill-considered cuts and I will do everything in my power to restore the Mars budget and to ensure American leadership in space exploration.”
In an interview with the San Gabriel Valley Tribune, Schiff said, “What they’re proposing will be absolutely devastating to planetary science and the Mars program. I’m going to be fighting them tooth and nail. Unfortunately if this is the direction the administration is heading, it will definitely hurt JPL – that’s why I’m so committed to reversing this.”
NASA still hopes for some type of scaled back Mars missions in the 2016 to 2020 timeframe which will be outlined in an upcoming article.
In the meantime, the entire future of America’s Search for Life on the Red Planet now hinges on NASA’s Curiosity Mars Science Laboratory rover speeding thru interplanetary space and a pinpoint touchdown inside the layered terrain of Gale Crater on August 6, 2012.
Venus as photographed by the Pioneer spacecraft in 1978. Some exoplanets may suffer the same fate as this scorched world. Credit: NASA/JPL/Caltech
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As the number of exoplanets being discovered continues to increase dramatically, a growing number are now being found which orbit within their stars’ habitable zones. For smaller, rocky worlds, this makes it more likely that some of them could harbour life of some kind, as this is the region where temperatures (albeit depending on other factors as well) can allow liquid water to exist on their surfaces. But there is another factor which may prevent some of them from being habitable after all – tidal heating, caused by the gravitational pull of one star, planet or moon on another; this effect which creates tides on Earth’s oceans can also create heat inside a planet or moon.
The findings were presented at the January 11 annual meeting of the American Astronomical Society in Austin, Texas.
The habitability factor is determined primarily by the amount of heat coming from the planet’s star. The closer a planet is to its star, the hotter it will be, and the farther out it is, the cooler it will be. Simple enough, but tidal heating adds a new wrinkle to the equation. According to Rory Barnes, a planetary scientist and astrobiologist at the University of Washington, “This has fundamentally changed the concept of a habitable zone. We figured out you can actually limit a planet’s habitability with an energy source other than starlight.”
This effect could cause planets to become “tidal Venuses.” In these cases, the planets orbit smaller, dimmer stars, where in order to be in that star’s habitable zone, they would need to orbit much closer in to the star than Earth does with the Sun. The planets would then be subjected to greater tidal heating from the star, enough perhaps to cause them to lose all of their water, similar to what is thought to have happened with Venus in our own solar system (ie. a runaway greenhouse effect). So even though they are within the habitable zone, they would lack oceans or lakes.
What’s problematic is that these planets could subsequently actually have their orbits altered by the tidal heating so that they are no longer affected by it. They would then be more difficult to distinguish from other planets in those solar systems which may still be habitable. While technically still within the habitable zone, they would have effectively been sterilized by the tidal heating process.
Planetary scientist Norman Sleep at Stanford University adds: “We’ll have to be careful when assessing objects that are very near dim stars, where the tides are much stronger than we feel on present-day Earth. Even Venus now is not substantially heated by tides, and neither is Mercury.”
In some cases, tidal heating can be a good thing though. The tidal forces exerted by Jupiter on its moon Europa, for example, are thought to create enough heat to allow a liquid water ocean to exist beneath its outer ice crust. The same may be true for Saturn’s moon Enceladus. This makes these moons still potentially habitable even though they are far outside of the habitable zone around the Sun.
By design, the first exoplanets being found by Kepler are those that orbit closer in to their stars as they are easier to detect. This includes smaller, dimmer stars as well as ones more like our own Sun. The new findings, however, mean that more work will need to be done to determine which ones really are life-friendly and which ones are not, at least for “life-as-we-know-it” anyway.
Beautiful view of our Milky Way Galaxy. If other alien civilizations are out there, can we find them? Credit: ESO/S. Guisard
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In the famous words of Arthur C. Clarke, “Any sufficiently advanced technology is indistinguishable from magic.” This phrase is often quoted to express the idea that an alien civilization which may be thousands or millions of years older than us would have technology so far ahead of ours that to us it would appear to be “magic.”
Now, a variation of that thought has come from Canadian science fiction writer Karl Schroeder, who posits that “any sufficiently advanced technology is indistinguishable from nature.” The reasoning is that if a civilization manages to exist that long, it would inevitably “go green” to such an extent that it would no longer leave any detectable waste products behind. Its artificial signatures would blend in with those of the natural universe, making it much more difficult to detect them by simply searching for artificial constructs versus natural ones.
The idea has been proposed as an explanation for why we haven’t found them yet, based on the premise that such advanced societies would have visited and colonized our entire galaxy by now (known as the Fermi Paradox). The question becomes more interesting in light of the fact that astronomers now estimate that there are billions of other planets in our galaxy alone. If a civilization reaches such a “balance with nature” as a natural progression, it may mean that traditional methods of searching for them, like SETI, will ultimately fail. Of course, it is possible, perhaps even likely, that civilizations much older than us would have advanced far beyond radio technology anyway. SETI itself is based on the assumption that some of them may still be using that technology. Another branch of SETI is searching for light pulses such as intentional beacons as opposed to radio signals.
But even other alternate searches, such as SETT (Search for Extraterrestrial Technology), may not pan out either, if this new scenario is correct. SETT looks for things like the spectral signature of nuclear fission waste being dumped into a star, or leaking tritium from alien fusion powerplants.
Another solution to the Fermi Paradox states that advanced civilizations will ultimately destroy themselves. Before they do though, they could have already sent out robotic probes to many places in the galaxy. If those probes were technologically savvy enough to self-replicate, they could have spread themselves widely across the cosmos. If there were any in our solar system, we could conceivably find them. Yet this idea could also come back around to the new hypothesis – if these probes were advanced enough to be truly “green” and not leave any environmental traces, they might be a lot harder to find, blending in with natural objects in the solar system.
It’s an intriguing new take on an old question. It can also be taken as a lesson – if we can learn to survive our own technological advances long enough, we can ultimately become more of a green civilization ourselves, co-existing comfortably with the natural universe around us.
View of Mars' surface near the north pole from the Phoenix lander. Polygon shapes can be seen in the soil. Credit: NASA/JPL-Calech/University of Arizona
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Mars is often referred to as a desert world, and for good reason – its surface is barren, dry and cold. While water was abundant in the distant past, it has long since disappeared from the surface, although ice, snow, frost and fog are still common. Other than liquid brines possibly trickling at times, all of Mars’ remaining water is now frozen in permafrost and in the polar ice caps. It has long been thought that the harsh conditions would make current life unlikely at best, and now a new study reaffirms that view.
The results come from continued analysis of the data from the Phoenix lander mission, which landed in the arctic region near the north pole of Mars in 2008. They suggest that Mars has experienced a prolonged drought for at least the past 600 million years.
According to Dr. Tom Pike from Imperial College London, “We found that even though there is an abundance of ice, Mars has been experiencing a super-drought that may well have lasted hundreds of millions of years. We think the Mars we know today contrasts sharply with its earlier history, which had warmer and wetter periods and which may have been more suited to life. Future NASA and ESA missions that are planned for Mars will have to dig deeper to search for evidence of life, which may still be taking refuge underground.”
The team reached their conclusions by studying tiny microscopic particles in the soil samples dug up by Phoenix, which had been photographed by the lander’s atomic-force microscope. 3-D images were produced of particles as small as 100 microns across. They were searching specifically for clay mineral particles, which form in liquid water. The amount found in the soil would be a clue as to how long the soil had been in contact with water. It was determined that less than 0.1 percent of the soil samples contained clay particles, pointing to a long, arid history in this area of Mars.
Since the soil type on Mars appears to be fairly uniform across the planet, the study suggests that these conditions have been widespread on the planet, and not just where Phoenix landed. It’s worth keeping in mind though that soil particles and dust on Mars can be distributed widely by sandstorms and dust devils (and some sandstorms on Mars can be planet-wide in size). The study also implies that Mars’ soil may have only been exposed to liquid water for about 5,000 years, although some other studies would tend to disagree with that assessment.
It should also be noted that more significant clay deposits have been found elsewhere on Mars, including the exact spot where the Opportunity rover is right now; these richer deposits would seem to suggest a different history in different regions. Because of this, and for the other reasons cited above, it may be premature then to extrapolate the Phoenix results to the entire planet, similar soil types notwithstanding. While this study is important, more definitive results might be obtained when physical soil samples can actually be brought back to Earth for analysis, from multiple locations. More sophisticated rovers and landers like the Curiosity rover currently en route to Mars, will also be able to conduct more in-depth analysis in situ.
The Phoenix soil samples were also compared to soil samples from the Moon – the distribution of particle sizes was similar between the two, indicating that they formed in a similar manner. Rocks on Mars are weathered down by wind and meteorites, while on the airless Moon, only meteorite impacts are responsible. On Earth of course, such weathering is caused primarily by water and wind.
As for the life question, any kind of surface dwelling organisms would have to be extremely resilient, much like extremophiles on Earth. It should be kept in mind, however, that these results apply to surface conditions; it is still thought possible that any early life on the planet could have continued to thrive underground, protected from the intense ultraviolet light from the Sun, and where some liquid water could still exist today.
Given Mars’ much wetter early history, the search for evidence of past or present life will continue, but we may have to dig deep to find it.
Comparison of the habitable zone around the Sun in our solar system and around the star Gliese 581. Credit: ESO
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Habitable zones are the regions around stars, including our own Sun, where conditions are the most favourable for the development of life on any rocky planets that happen to orbit within them. Generally, they are regions where temperatures allow for liquid water to exist on the surface of these planets and are ideal for “life as we know it.” Specific conditions, due to the kind of atmosphere, geological conditions, etc. must also be taken into consideration, on a case-by-case basis.
Now, by examining trace elements in the host stars, researchers have found clues as to how the habitable zones evolve, and how those elements also influence them. To determine what elements are in a star, scientists study the wavelengths of its light. These trace elements are heavier than the hydrogen and helium gases which the star is primarily composed of. Variations in the composition of these stars are now thought to affect the habitable zones around them.
The study was led by Patrick Young, a theoretical astrophysicist and astrobiologist at Arizona State University. Young and his team presented their findings on January 11, 2012 at the annual meeting of the American Astronomical Society in Austin, Texas. He and his colleagues have examined more than a hundred dwarf stars so far.
An abundance of these elements can affect how opaque a star’s plasma is. Calcium, sodium, magnesium, aluminum and silicon have been found to also have small but significant effects on a star’s evolution – higher levels tended to result in cooler, redder stars. As Young explains, “The persistence of stars as stable objects relies on the heating of plasma in the star by nuclear fusion to produce pressure that counteracts the inward force of gravity. A higher opacity traps the energy of fusion more efficiently and results in a larger radius, cooler star. More efficient use of energy also means that nuclear burning can proceed more slowly, resulting in a longer lifetime for the star.”
The lifetime of a star’s habitable zone can also be influenced by another element – oxygen. Young continues: “The habitable lifetime of an orbit the size of Earth’s around a one-solar-mass star is only 3.5 billion years for oxygen-depleted compositions but 8.5 billion years for oxygen-rich stars. For comparison, we expect the Earth to remain habitable for another billion years or so, for about 5.5 billion years total, before the Sun becomes too luminous. Complex life on Earth arose some 3.9 billion years after its formation, so if Earth is at all representative, low-oxygen stars are perhaps less than ideal targets.”
As well as the habitable zone, the composition of a star can determine the eventual composition of any planets that form. The carbon-oxygen and magnesium-silicon ratios of stars can affect whether a planet will have magnesium or silicon-loaded clay minerals such as magnesium silicate (MgSiO3), silicon dioxide (SiO2), magnesium orthosilicate (Mg2SiO4), and magnesium oxide (MgO). A star’s composition can also play a role in whether a rocky planet might have carbon-based rock instead of silicon-based rock like our planet. Even the interior of planets could be affected, as radiocative elements would determine whether a planet has a molten core or a solid one. Plate tectonics, thought to be important for the evolution of life on Earth, depend on a molten interior.
Young and his team are now looking at 600 stars, ones that are already being targeted in exoplanet searches. They plan to produce a list of the 100 best stars which could have potentially habitable planets.
As it turns out, about a third of the lake beds examined still show evidence for clay deposits. A total of 79 lake beds out of 226 studied to be exact, indicating that they are less common on Mars than on Earth. The reason for this may be that the chemistry of the water was not ideal for preserving clays or that the lakes were relatively short-lived.
