The Kepler space telescope, which has discovered most of the new exoplanets, detects them only by the fact that they eclipse their home stars, causing the stars to slightly dim. This is like detecting a moth flying in front of a distant streetlamp by the fact that the light intensity dips somewhat. Kepler cannot take photos of these planets.
Even with the largest telescopes in the world, taking a picture of any Earth-size exoplanet is currently impossible, although some larger planets have been imaged. The exoplanets are very distant. The nearest exoplanet is in orbit around the star Alpha Centauri, which is more than 4 light-years from Earth.
With our current technology, it would require about thousand years for a probe to travel that far. No, it is hard to imagine humans travelling beyond our own Solar System in the foreseeable future. A trip to even the nearest star would require many generations, and the energy needed for such a starship to reach its destination within the lifetime of the crew is far beyond anything we can muster.
Europa, one of the four largest moons of Jupiter, has more liquid water than all the oceans of the Earth. The presence of liquid water and a source of heat produced by its gravitational interaction with Jupiter to keep that water warm makes Europa a very attractive world on which to look for life.
We have data from the Voyager and Galileo spacecraft, but these neither went into orbit around Europa nor did they land. The biggest challenge for exploring its ocean is reaching the liquid water, which lies beneath a crust of ice frozen more solid than granite.
The crust is 10 km or more thick. These two moons of Saturn are also appealing to scientists trying to find life on other worlds. Enceladus, like Europa, has a large body of water in its interior, and the push and pull of gravitational interaction with Saturn squirts some of this water into space.
A spacecraft could conceivably grab samples of this cryovolcano, and see if there are any microbes in the water. Titan is the only world in the Solar System known to have liquid lakes on its surface … but they are lakes of liquid methane and ethane, not water.
No, Curiosity is investigating the habitability of Mars, and in particular is looking for geological evidence of past water and of organic compounds that might tell us that Mars once had life, perhaps billions of years ago. The only mission that directly searched for life on Mars was Viking, back in Two landers carried biology instruments designed to look for evidence of microbes in the soil. The results were interpreted by the majority of the Viking biology team as being negative, and we now know that conditions in the surface soil where the lander collected its samples could not support Earth-like life.
We think that if there are living microbes on Mars, they are probably at least several meters below the surface, in special environments where liquid water is present. The Curiosity rover is not able to drill down that deep, nor do we know where such habitable conditions might be found.
Perseverance, which is part of the Mars mission to the Red Planet, will look for soil samples that might contain evidence of microbial life that existed on Mars billions of years ago.
It is doing this reconnaissance in Jezero Crater, which was once a lake fed by two, now-dry rivers. The samples will be packaged up by Perseverance, and eventually brought back to Earth for detailed analysis by a spacecraft that will be sent to Mars within a few years.
Scientists take careful steps to minimize such forward contamination on any Mars lander. We can allow this degree of microbial contamination since we know that the surface of Mars is not able to support living organisms from Earth, being very dry, cold, and stung by lethal ultraviolet light.
Therefore, we are confident that microbes from Earth will not grow on the surface and contaminate the planet. Phosphorus is one of a handful of essential elements for life as we know it on Earth.
This element is part of the molecular backbone of DNA, and plays a key role in the storage and transfer of chemical energy within cells. Arsenic is an element with a similar atomic structure to phosphorus, but is not important in biochemistry.
In large quantities it is a well-known poison. Geological Survey. Recent results by other scientists have shown that there was no arsenic in the DNA of this microbe. The ability of this microbe to tolerate arsenic is interesting to astrobiologists, but it is not as dramatic a discovery as the popular article suggested.
We are already seeing many impacts of global warming. The rapid shrinking of the arctic icecap has opened the Northeast Passage to shipping, and cruise ships already book passengers for voyages through the Northwest Passage.
The melting arctic ice and permafrost are exposing oil and mineral deposits for exploitation, but also endangering arctic wildlife. Most important, the melting of arctic snow and ice darkens the surface, leading to more rapid warming during the summer and a shift in weather patterns over North America. Melting of ice from Greenland and Antarctica is also contributing to sea level rise, making destructive storms like Hurricane Sandy in much more likely.
Severe droughts in the U. Within a few years, the accelerating loss of ice from the Himalayas is expected to lead to the summer drying up of several great Asian rivers, which are the source of water for more than a billion people in China, India, Pakistan, and Bangladesh. By the middle of the century, rising sea levels and stronger storms are likely to lead to the permanent evacuation of much of New Orleans, New York, Miami, Amsterdam, and Venice.
The current rapid global warming on Earth is due to the burning of fossil fuels, hydrocarbons like oil, gas, and coal. We are releasing carbon into our atmosphere that was produced by plants and buried millions of years ago. As far as we know, Mars has no such carbon deposits. Without large quantities of oil, gas or coal to burn, and also no atmospheric oxygen to do the burning, we have no easy way of warming Mars as we are now doing on Earth.
One suggestion for producing a temporary warming on Mars would be to re-direct a large comet so that it hits the polar areas of Mars, releasing a great deal of water and carbon dioxide.
But the fundamental problem with Mars is that its mass is too small to hold on to a substantial atmosphere for very long. It is these fragile environments near the poles and also in high mountains that are most sensitive to climate change. Additionally, they also constitute important analogs for conditions on our neighboring world, Mars.
Institute researchers do extensive field work in the Arctic including a research station on Devon Island , in the Antarctic including exploratory dives under the ice in the dry valleys , and in the high Andes mountains of South America where the rapid retreat of glaciers is changing the entire ecosystem.
We expect to carry out long-term studies of these environments and the changes in their biota under environmental stress. This research may also help us interpret the history of climate change on Mars over hundreds of millions of years. Life exists deep underground and inside rocks in the Antarctic.
There is a comprehensive listing of extremophile record-holders on Wikipedia. And all of it has DNA. Giant planets do not have a solid surface, one you could stand on. Uranus and Neptune are more mysterious as scientists have less data than for Jupiter and Saturn. Nonetheless, we also think that those planets do not have a solid surface. Such a planet sometimes called Nemesis , always staying on the opposite side of the Sun from the Earth, would not be in a stable orbit.
Perhaps more to the point, if there were anything there, its presence would be easily detected by its gravitational effects on the orbits of other planets, asteroids, and comets.
And of course, it would have been seen by many of our planetary space probes. For more information on this history of this idea, look up "counter-earth" in Wikipedia. A less problematic question is to ask when the oceans will evaporate, as the Earth enters a runaway greenhouse state. A recent French study predicts that the oceans will turn to steam approximately one billion years in the future. That time scale is so long that it does not really mean much to most of us. The current rapid warming from human-caused climate change is an immediate problem that requires action today, unlike the gradual luminosity increase of the Sun due to the compositional changes taking place in its fusing core.
Even 18th century astronomers speculated that the white polar caps of Mars might be composed of water ice a speculation that is only partially true. Scientists also regularly monitor water vapor in the atmosphere. The Viking 2 lander photographed winter frost on the surface in the s, and the Phoenix lander found and photographed ice deposits in All of the Mars orbiters since the s have photographed water erosion features, ranging from huge outflow channels to small, recently made gullies in crater walls.
Where did the water that made these erosion features go? Some think that water is present now as ice, including large polar deposits. Scientists also think there are very large water deposits below the surface, with ice permafrost on top and likely liquid water aquifers at depth. Some water escaped along with the rest of the early Martian atmosphere, but most of it is still there.
The problem with Mars is not a lack of H 2O, but low temperatures. Those are consequence of the loss of much of its atmosphere and the resultant diminution of any greenhouse effect. Although we often speak of finding water on the Moon, this terminology is confusing. What we have found during the course of several recent missions is ice in permanently shadowed polar craters, presumably deposited by incoming asteroids.
There is also new evidence of chemically bound water molecules in the lunar soil. However, we have not found liquid water, which is as far as we know required for life. If there were liquid water at the lunar surface, it would instantly evaporate because of the low lunar gravity and the absence of an atmosphere.
Ice is stable in permanently shadowed polar craters only because the temperatures are extremely low. It is colder on the floors of some of these craters than on the surface of Pluto.
Thus, we have not found anything on the Moon that would encourage us to look for evidence of life there. Shadow biosphere is the name given by scientists to a hypothetical microbial biosphere of Earth that would use radically different biochemical and molecular processes than the terrestrial life we know.
So far, there is no compelling evidence for a real shadow biosphere on Earth, but by definition it would be difficult to detect with our usual biochemical tools. One reason for skepticism about its existence is the evolutionary fact that stronger life forms tend to out-compete weaker ones, leading to the extinction of the weaker form.
Thus, we would have to wonder how two different biospheres could have coexisted on this planet for four billion years. Searching for a shadow biosphere might be useful to help us think about how we could identify an alien biosphere on other worlds.
Sometimes the meaning is expanded to include any life that is based on the same sort of water-mediated carbon chemistry with amino acids and proteins that we have on Earth, but with some other inheritance mechanism that does not use DNA or RNA. However, even in this bitter cold, hydrocarbons like methane and ethane are liquid, and might conceivably form the basis for carbon-based life very different from that on Earth. No one knows whether life emerges on a planet whenever conditions are favorable.
The only example of life we have is on our own planet. It is entirely possible that life has begun several times on Earth, but early biology might have been obliterated, perhaps repeatedly, by impacts of some of the large rocks that were flying around the early solar system, remnants of planetary formation. Larger meteors would produce impacts with sufficient energy to boil the oceans, a circumstance guaranteed to destroy any early life.
Mars, with lower gravity, has an atmosphere much less than ours. The Moon, which has lower gravity still, has no atmosphere. The magnetic field plays very little role. Venus, with no magnetic field, actually has a much thicker atmosphere than Earth.
The presence of oxygen as a major component of our atmosphere is a consequence of photosynthetic life, which produces oxygen as a byproduct. One-third of the American public and a similar fraction of the citizenry in other countries is convinced that extraterrestrials may be buzzing the countryside in their spacecraft, or occasionally alighting in the back yard to abduct a few humans for breeding experiments.
The presence of aliens on our planet is not something you would want to hide: it would be the biggest science story of all time, and tens of thousands of university researchers would be working away on it. However, despite the popularity of aliens in both movies and TV, and more than 70 years of UFO sightings, the lack of credible physical evidence has made it difficult for serious scientists to believe that UFOs have anything to do with extraterrestrial visitors.
Note that witness testimony, which is much ballyhooed in the media, has little horsepower when it comes to swaying scientists. Other SETI searches look for flashing laser pulses.
We now know that planets are present in most stellar systems, and on the basis of evidence collected so far can estimate that there are many billions of Earth-size worlds in the Galaxy. No SETI search has yet received a confirmed, extraterrestrial signal. If we had, the world would know about it. YOU would know about it! There is no policy of secrecy and any promising signal would quickly prompt observations at other observatories to confirm that it was real.
In the past, there were several unexplained and intriguing signals detected in SETI experiments. Who would believe cold fusion unless many researchers could duplicate it in their labs? The same is true of extraterrestrial signals: they are credible only when they can be found more than once.
Narrow-band signals — perhaps only a few Hertz wide or less — are the mark of a purposely built transmitter. Natural cosmic noisemakers, such as pulsars, quasars, and the turbulent, thin interstellar gas of our own Milky Way, do not make radio signals that are this narrow.
The static from these objects is spread all across the spectrum. Keep in mind that the receivers used for SETI are designed to detect constant or slowly pulsed carrier signals … something like a flute tone played against the noise of a waterfall. This is because — to gain sensitivity — SETI receivers average the incoming signals for seconds or minutes. Fortunately, once a detection is made, we expect the money will become available to do so.
We can pinpoint the spot on the sky where the signal is coming from, and slow changes in its frequency will tell us something about the rotation and orbital motion of E.
But even though this information is limited, the detection of alien intelligence would be an enormously big story. And of course, there will be a clamor to build the big dishes that would allow us to pick up E. No one knows. That would make real back-and-forth communication tedious at best, so these alien broadcasters might be tempted to send lots of information, and in a format that we could eventually decipher. Then again, we might pick up a signal that was never intended for us, in which case it might be impossible to figure out.
The cost of the program was less than 0. Current SETI searches are funded by donations, mostly from individuals and a few foundations and corporations. There is relatively little background static from galaxies, quasars, high-speed charged particles, and other cosmic noise makers in the microwave part of the spectrum. This makes faint signals easier to pick out. Every radio astronomer including extraterrestrial ones will know about these emissions.
On the other hand, these same frequencies might be avoided by E. At the Allen Telescope Array , we hedge our bets by observing at all frequencies between 1 and 9 GHz i. The main feature distinguishing signals produced by a transmitter from those produced by natural processes is their spectral width, i.
Any signal less than about Hz wide must be, as far as we know, artificially produced. Such narrow-band signals are what most radio SETI experiments look for. Other tell-tale characteristics include a signal that is completely polarized or the existence of coded information on the signal. Unfortunately, SETI searches are burdened with confusion caused by narrow-band, polarized, and coded signals from our own planet. Military radar and telecommunications satellites produce such signals.
The Allen Telescope Array sorts out these confusing signals by comparing the cosmic static received from one part of the sky with that from another.
Historically, SETI researchers have looked for narrow-band signals, the type that are confined to a small usually 1 Hz or less spot on the dial. What if E. Would our searches pick up his call? That depends. If the signal is strong enough, it might be detected with ordinary SETI equipment, although weak broadcasts will be missed.
Modern SETI experiments have tried to refine their receiving systems to be sensitive to these other types of communications. If they wish to get in touch or, for example, simply have high-powered radars for finding incoming comets, they will generate the type of signals our experiments can find. To date, the SETI Institute has conducted only passive experiments, designed to listen for signals, not to send them.
However, humankind has been unintentionally transmitting signals into space — primarily high-frequency radio, television, and radar — for more than seventy years.
Our earliest TV broadcasts have reached several thousand nearby stars, although any alien viewers would have to build a very large antenna to detect them. One reason that SETI researchers have not chosen to broadcast is because of the long time one has to wait for a reply. If the nearest civilization is light-years away, we would have to sit around for years before we could expect a response. Nonetheless, a few intentional messages have been sent. One message, transmitted in from the Arecibo Observatory, was a simple picture describing our solar system, the compounds important for life, the structure of the DNA molecule, and the form of a human being.
The message was transmitted in the direction of the globular star cluster M13, about 25, light years away. Since then, both NASA and a small group in Russia have sent several relatively brief, deliberate signals into space. It has to date organized one transmitting session using an antenna in Norway. In general, no. Most earthly transmissions are too weak to be found by equipment similar to ours at the distance of even the nearest star.
But there are some important exceptions. High-powered radars and the Arecibo broadcast of which lasted for only three minutes could be detected at distances of tens to hundreds of light-years with a setup similar to our best SETI experiments. The stars are simply too far away.
Our best rockets travel at about 10 miles per second. Even to reach the nearest other star system, Proxima Centauri, at about 4. There are several thousand stars within light-years of us. To investigate them all with spacecraft would take millions of years and vast amounts of money. A better scheme is to search for radio waves which travel at the speed of light using state-of-the-art technology, and at a relatively modest cost. For the extraterrestrials to know, we would have to send a message in reply.
Visible light has a higher frequency than radio waves, allowing more data to be encoded over any given period of time. Like radio waves, visible light also filters through our atmosphere, making it a logical portion of the spectrum for SETI searches. In , Horowitz and The Planetary Society constructed a 1.
The search is still in operation, completing a full survey of the sky visible from Massachusetts every nights. The program has undergone many upgrades and relocations over the years, and was still running at Arecibo when the telescope was damaged by Hurricane Maria in September There were more data available than could be processed using supercomputers, said Dan Werthimer, who in was the chief scientist of the Berkeley SETI Research Center.
Werthimer and three other engineers and scientists designed a program to allow home computers to help with the data crunching. We want to get behind it. In , Berkeley released the result, [email protected]. Until the project's end in , more than 5.
The open-source software, BOINC, on which [email protected] is based, is now used for other projects.
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