Is there life on other planets and if so how frequent?

Is there life on other planets and if so how frequent?

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Some shed tears of joy as the news about the successful landing of the Mars Rover Curiosity came in. Then the most comprehensive 3D map of our observable universe was published. 2012 is literally an astronomical year.

As an layman I would like to know about scientists current understanding about the frequency models that life forms on other planets?

See also:

OK, so we know a couple of things about life in the universe. Note, however, that this is not really an answer and is also not very biological in nature.

So, we don't know how life began on the Earth. However, do know that:

  1. The probability of life evolving on a planet in the universe is non-zero (since we exist) and,
  2. So far, we have not found evidence for life elsewhere in the universe.

So this leaves us with two main possibilities:

  • Life is rare in the universe.
  • Life is common in the universe but for some reason we do not detect it.

This latter possibility is basically a restatement of the Fermi Paradox which says

"The universe is very big and there should be lots of alien life out there. Where is everybody?"

In the case that life is common, we can speculate extensively on why we have not detected it so far. For example:

  • We haven't been looking long enough (SETI has been running for only a few decades)
  • We haven't been looking hard enough (the budget of SETI etc. is not large)
  • We haven't been looking in the right way. We are currently looking mainly in the radio regime, maybe aliens broadcast in X (where X is part of the E/M spectrum or something else entirely, e.g. gravity waves, tachyons)
  • Life is common, but intelligent life is rare (this would be my guess)
  • Life is common and intelligent, and doesn't want to answer (why? ask a xenopsychologist)

OK, so these are just some examples of "solutions" to the Fermi Paradox. There are many more which are much more exotic. My personal favourite of these is that we live in a simulated universe and the coders have not included additional alien life in the simulation. It would explain some strange "coincidences" about fundamental physical constants, but what simulation, no matter how good, would ever come up with cauliflower cheese for example?

However, until we actually detect life on another planet we will still be in the dark. The next generation of telescopes will be able to do this for nearby exoplanets if life is present on them and has affected the biosphere in a detectable way.

Edit - You mention "frequency models", but all we can currently say is that the probability of life on other planets is not zero - due to our existence - as I mentioned at the start

Some references:

According to this, 1.2% of stars have planets that can support life. According to Google, there are 300,000,000,000 stars in the Milky Way. That means 3,600,000 stars can support life. Each of these stars is estimated to have 1-2 planets that can support life. For the sake of simplicity, I'll use 1.5 to represent this, since it is the average of 1 and 2. 1.5×3,600,000=5,400,000 planets capable of supporting life. Looking around the web, there are wildly different estimates of the odds of life evolving on one of these planets (from 1%-100%), but 100% seems like the most common. This means that, statistically, the odds of extraterrestrial life existing are extremely high.

Are Aliens Real? Is There Life on Other Planets?

In 2040, Americans plan to vote in a U.S. presidential election. Japan promises to stop using nuclear power. Britain’s Prince George will turn the ripe age of 27. And, as the interactive above demonstrates, the world is likely to find alien life. It could happen even sooner, depending how many civilizations are out there to be found. To understand why this is, it helps to know about someone name Frank Drake.

Drake is the least lonely man on Earth—if not in the entire galaxy. Most of us are reserving judgment on whether there is intelligent life on other planets we haven’t even found bacteria yet, much less a race of aliens with Internet service and takeout food. But Drake, an astrophysicist and chairman emeritus of the California-based SETI (Search for Extraterrestrial Intelligence) Institute, has no such doubts.

It was in 1961, when he was working at the National Radio Astronomy Observatory in Green Bank, W. Va., that Drake developed the eponymous—and now famous—Drake Equation, which calculates how many advanced and detectable civilizations there should be in the Milky Way in any one year. The number turns out to be potentially huge, and while it’s admittedly based on a number of Earth-centric suppositions—the collapse of any one of which calls much of the equation into question—all of those suppositions are based in increasingly solid science.

Start with the number of stars in our galaxy, which is conservatively estimated at 100 billion, though is often cited as three times that. Of those 100 billion, from 20% to 50% probably harbor planetary systems—an estimate that becomes more and more reliable as the Kepler Space Telescope and various ground-based observatories detect increasing numbers of exoplanets.

Not all of those exoplanets would be capable of sustaining Earth-like life, so the equation assumes from 1 to 5 in any system could. Of those bio-friendly worlds, from 0% to 100% would actually go on to develop life. And of those world, in turn, from 0% to 100% would develop life forms that we would consider intelligent.

The mere existence of intelligent life forms tells us nothing, however, unless they have the ability to make themselves known—which means to manipulate radio waves and other forms of electromagnetic signaling. Drake estimates that from 10% to 20% of the smart civilizations would clear that bar.

Finally, and perhaps most anthropocentrically, the equation considers how long any one of those semaphoring civilizations would be around to blink their signals our way. A sun like ours survives for about 10 billion years life on Earth has been around for only about 3.5 billion years, and humans have been radio-capable for barely a century.

If we destroy ourselves in an environmental or nuclear holocaust tomorrow, our signal will go dark then. If we survive for tens of thousands of years, we will be announcing our presence to the cosmos for far longer—and the same is true of all of the other civilizations that live in the Milky Way.

Factor all of this together and stir in a little statistical seasoning concerning our increasing ability to study other star systems for signals, and, as the above interactive shows—the results can vary wildly. If you play the game conservatively—lowballing all of the variables—you might get about 1,000 detectable civilizations out there at any given time. Play it more liberally and you get hundreds of millions. The interactive let’s you play that game yourself. Imagine there are 10,000 detectable civilizations and we are likely to find alien life by 2040. If there are a million, we’d discover alien life by 2028.

Nobody pretends the Drake Equation is the final word. Even its enthusiasts admit that it is, at best, a way to “organize our ignorance.” But organized ignorance is a whole lot better than the disorganized kind and it is, almost always, a starting point toward wisdom.


Astronomers looking for alien signals have examined only a few thousand star systems so far. But as SETI Institute senior astronomer Seth Shostak has noted, the rate at which researchers are able to process the massive amounts of data that radio telescopes receive doubles approximately every 18 months to two years, meaning it grows by a factor of ten every six years or so.

The Milky Way has around 100 billion (10 11 ) star systems that could conceivably host intelligent life under our current assumptions. An estimate of 100,000 (10 5 ) active civilizations in the galaxy would mean one per million star systems. At the exponential rate of growth in signal processing, researchers will have examined one million candidates by around 2034, bringing the odds of a discovery into the probable. Adding or removing a zero from the estimate of the number of civilizations out there merely adds or subtracts six years from the estimate, respectively, since that’s how long it takes to expand our search proportionally. See you in 2040, aliens.

Tiny UFOs

Over the last four billion years, Earth has received a number of visitors from Mars. Our planet has been bombarded by rocks blown from the surface of the red planet, one of the few bodies in the solar system scientists have samples from. Of the 34 Martian meteorites, scientists have determined that three have the potential to carry evidence of past life on Mars.

A meteorite found in Antarctica made headlines in 1996 when scientists claimed that it could contain evidence of traces of life on Mars. Known as ALH 84001, the Martian rock contained structures resembled the fossilized remains of bacteria-like lifeforms. Follow-up tests revealed organic material, though the debate over whether or not the material was caused by biological processes wasn't settled until 2012, when it was determined that these vital ingredients had been formed on Mars without the involvement of life.

"Mars apparently has had organic carbon chemistry for a long time," study lead author Andrew Steele, a microbiologist at the Carnegie Institution of Washington, told

However, these organic molecules formed not from biology but from volcanism. Despite the rocky origin for the molecules, their organic nature may prove a positive in the hunt for life.

"We now find that Mars has organic chemistry, and on Earth, organic chemistry led to life, so what is the fate of this material on Mars, the raw material that the building blocks of life are put together from?" Steele said.

Scientists also found structures resembling fossilized nanobacteria on the Nakhla meteorite, a chunk of Mars that landed in Egypt. They determined that as much as three-fourths of the organic material found on the meteorite may not stem from contamination by Earth. However, further examination of the spherical structure, called an ovoid, revealed that it most likely formed through processes other than life.

"The consideration of possible biotic scenarios for the origin of the ovoid structure in Nakhla currently lacks any sort of compelling evidence," the scientists wrote in a study in the journal Astrobiology. "Therefore, based on the available data that we have obtained on the nature of this conspicuous ovoid structure in Nakhla, we conclude that the most reasonable explanation for its origin is that it formed through abiotic [physical, not biological] processes."

A third meteorite, the Shergotty, contains features suggestive of biofilm remnants and microbial communities.

"Biofilms provide major evidence for bacterial colonies in ancient Earth," researchers said in a 1999 conference abstract. "It is possible that some of the clusters of microfossil-like features might be colonies, although that interpretation depends on whether the individual features are truly fossilized microbes."

All of these samples provide tantalizing hints of the possibility of life in the early history of the red planet. But a fresh examination of the surface has the potential to reveal even more insights into the evolution of life on Mars.

7 Good Reasons Why There Might Be Life on Other Planets

We have no direct evidence (yet) that there is life on other planets, moons, or in interstellar space. Nevertheless, there are some compelling reasons to believe that eventually we will discover some, perhaps even in our own solar system. Here are seven reasons why scientists believe that life is out there, just waiting to meet us. It might not be green-skinned ladies in silver saucers, but it will be alien.

1. Extremophiles on Earth
One of the big questions is whether life could evolve and survive on a world radically different than Earth. The answer appears to be yes, if you consider that even Earth harbors extremophiles , or organisms that can survive in extremes of heat, cold, poisonous (to us) chemicals, and even in vacuum. We've found creatures who live without oxygen around the edges of super-heated volcanic vents at the bottom of the ocean, and we've found life in the brackish pools of the high Andes, as well as the ice-covered lakes of the arctic . There are even tiny creatures called tardigrades that can survive in the vacuum of space. So we have direct evidence that life can thrive in pockets of alien atmosphere on Earth. In other words, we know life can survive in conditions we've seen on other planets and moons. We just haven't found it yet.

Extremophiles I Have Known And Loved

Extremophiles challenge everything we thought we knew about the existence of life on Earth. Now,…

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As unbelievable as it sounds, it's thought that up to a third of all the Earth's organisms by mass

These creatures live in a lake that's been sealed beneath ice for 2,800 years

Antarctica's Lake Vida has been sealed beneath the ice for 2,800 years. Its depths have become a…

2. Evidence of chemical precursors to life on other planets and moons
Life on Earth probably evolved from chemical reactions that eventually formed cellular membranes and proto-DNA. But those original chemical reactions may have started with complex organic compounds — such as nucleic acids, proteins, carbohydrates, and lipids — in the atmosphere and ocean. There is evidence that these "precursors to life" exist on other worlds already. Titan has some in its atmosphere , and astronomers have spotted them in the rich environment of the Orion Nebula too . Again, we haven't actually found life, but we've found the ingredients that many scientists believe contributed to the development of life on Earth. If those ingredients are common throughout the universe, it's likely that life has emerged in places other than our home planet.

3. Rapidly-expanding number of Earthlike planets
Over the past decade, planet hunters have found hundreds of exoplanets, many of them gas giants like Jupiter. But new techniques for planetary detection have allowed them to detect smaller, rocky worlds like Earth. Some are even in the "Goldilocks zone" around their stars , meaning they orbit at a distance that could produce temperatures similar to those on Earth. Given how common exoplanets beyond our solar system have turned out to be, it seems likely that one of them plays host to some form of life.

Potentially habitable "Super-Earth" is among 50 newly discovered exoplanets

HD 85512 b is a rocky planet about 3.6 times the mass of Earth, located right at the edge of its…

4. Sheer diversity and tenacity of life on Earth
Not only did life evolve on Earth under extremely difficult conditions, but it somehow managed to survive megavolcanoes, meteorite strikes, ice ages, droughts, ocean acidification, and radical atmospheric changes. We've also seen incredible diversity of life on our planet in a relatively short period of time, geologically speaking. Life is pretty tenacious. Why couldn't it take hold on one of Saturn's moons, or in another star system?

5. Mysteries surrounding how life originated on Earth
Though we have theories about how life originated on Earth, involving those complex carbon molecules I mentioned earlier, there is ultimately a mystery about how those chemicals came together to form fragile membranes that eventually became cells. This mystery has been deepened the more we know about how incredibly hostile the environment on Earth was when life evolved — the atmosphere was packed with methane, and the planet's surface boiled with lava. One common theory is that simple, single-celled life actually evolved elsewhere — perhaps Mars — and came to Earth inside meteorites. This theory is called panspermia , and suggests that life on Earth arose due to life on other planets.

Could aliens have created life on Earth?

We know a lot about the history of life on Earth, but how it began is still one of our greatest…

6. Growing evidence that oceans and lakes are common, at least in our solar system
Life on Earth originated in the ocean, so it follows that this might be the case on other worlds. Now there is strong evidence that water once flowed freely on Mars , and Saturn's moon Titan has seas of methane as well as rivers flowing across its surface. Jupiter's moon Europa is believed to be one, massive ocean , warmed by the moon's core and completely covered in a thick, protective layer of ice. Any of these worlds might have harbored life at one time, or currently.

Mars once had water warm enough to sustain life

We know that Mars once had lots of water, considered a prerequisite for habitability. What hasn't…

Top 10 Proof Of Alien Life On Other Planets

Is there any form of life in various other parts of the Universe? This is certainly one of the popular questions within the mind of the astronauts, scientists and even common people. To give an answer to this question, below are discussed about top 10 proof of alien life on other planets.

(1) Image of a workman on Mars

Pictures captured by Mars Curiosity Rover certainly prove that there is alien life on Mars. The image shows the shadow of a human like figure who was working on a space craft. Even though the unidentified being was wearing a suit commonly worn by the human astronauts but it was certainly without a helmet. Since humans cannot leave in the toxic environment of Mars, it certainly proves that the unidentified being was an alien.

(2) Existence of Aliens on Europa, Jupiter’s beautiful moon

According to sources, this is also one of the prime locations of the aliens. For more than 20 years, astrobiologists have been researching to gather vital information about existence of life on Europa, Jupiter’s beautiful moon. Researchers claim that one of the major reasons behind existence of life in this place is due to the tidal energy exerted on Europa by the powerful gravitational force of Jupiter. Christopher McKay, senior space scientists in Astrobiology Division at NASA Ames Research Center and Space Science claims that Europa is the best place for alien existence.

(3) Alien Autopsy Photos

The alien autopsy photos that have been captured by Area 51 certainly prove that there is existence of alien life on other planets. Later on, the autopsy photos became major evidence after Tom Carey, a UFO expert and Kodak verified that images were real and no Photoshop software has been used to create them.

(4) Fish shaped alien peeking out of the cave on Mars

This is a terrific incident that has been captured by the NASA’s Curiosity Rover. Scott C Waring, one of the renowned UFO researcher claims that a fish shaped alien was continuously peeking through the cave on Mars. He also alleged that the rover has also been able to capture a video of a crashed drone besides the cave. This certainly proves that there is existence of alien life on Mars.

(5) Existence of primitive alien on Titan

Research conducted by various renowned scientists has highlighted that there is evidence of life on Titan, the biggest moon of planet Saturn. They have also been able to discover that the primitive aliens are breathing on the atmosphere of Titan and thereby there is a gradual decrease in the level of hydrogen from the surface of the moon.

(6) Alien life on Pluto

According to photos released by NASA on October 2015, there is evidence of alien existence on Pluto. UFO highlights that the images captured on Pluto proves that a giant alien ship has been parked on the Blue Ridge Mountain of this planet,

(7) Astronauts on Apollo 11 detected a rocket flying alongside

The astronauts on Apollo 11 sent a message to the control room to get an idea whether S-4B, the detached part of the rocket was still nearby. This unusual question was asked by them after they were able to detect that something was flying along side of their rocket. Later, they were able to determine that it was a space craft of some unidentified visitor.

(8) Presence of alien on Enceladus

According to various researches conducted by NASA, it has been found that there is a huge body of water beneath the Enceladus, sixth largest moon of Saturn. Scientists further highlight that if there is an existence of water beneath this moon then there must be existence of aliens in this place.

(9) Mysterious signals received during the SETI project

In the year 2003, when astronauts were in search of extraterrestrial life using massive telescope received a high frequency radio signals that disappeared suddenly, except one that became stronger. This signal is evidence that there is alien life in other planet.

(10) Evidence of life on Venus

According to a research conducted by famous Russian astronaut, it has been found that there is existence of life in the planet Venus. Photographs captured on the space highlight that there is existence of several forms life on Venus.

Plate Tectonics Could be Essential for Life

Plate tectonics is the process of continents on the Earth drifting and colliding, rock grinding and scraping, mountain ranges being formed, and earthquakes tearing land apart. It makes our world dynamic and ever-changing. But should it factor into our search for life elsewhere in the universe?

Tilman Spohn believes so. As director of the German Space Research Centre Institute of Planetary Research, and chairman of ESA&rsquos scientific advisory committee, he studies worlds beyond our Earth. When looking into the relationship between habitability and plate tectonics, some fascinating possibilities emerged.

Knowing where to look

It is thought that the best places to search for life in the Universe are on planets situated in &ldquohabitable zones&rdquo around other stars. These are orbital paths where the temperature is suitable for liquid water not so close to the star that it boils away, and not so far that it freezes. Spohn believes that this view may be outdated. He elaborates, &ldquoyou could have habitats outside those, for instance in the oceans beneath ice covers on the Galilean satellites, like Europa. But not every icy satellite would be habitable. Take Ganymede, where the ocean is trapped between two layers of ice. You are missing a fresh supply of nutrition and energy.&rdquo

So planets and moons that lie beyond habitable zones could host life, so long as the habitat, such as an ocean, is not isolated. It needs access to the key ingredients of life, including hydrogen, oxygen, nitrogen, phosphorous and sulphur. These elements support the basic chemistry of life as we know it, and the material, Spohn argues, must be regularly replenished. Nature&rsquos method of achieving this on the Earth appears to be plate tectonics.

Plate tectonics &ndash essential for life?

It is an idea growing in popularity among planetary scientists. Says Spohn, &ldquoplate tectonics replenishes the nutrition that primitive life could live on. Imagine a top surface that is depleted of the nutrition needed for bacterial life. It needs to be replenished, and plate tectonics is a method of achieving this.&rdquo

Spohn found that the further he delved into the issue, the more important plate tectonics seemed to be for life. For example, it is believed that life developed by moving from the ocean to the kind of strong and stable rock formations that are the result of tectonic action. Plate tectonics is also involved in the generation of a magnetic field by convection of Earth&rsquos partially molten core. This magnetic field protects life on Earth by deflecting the solar wind. Not only would an unimpeded solar wind erode our planet&rsquos atmosphere, but it also carries highly energetic particles that could damage DNA.

Another factor is the recycling of carbon, which is needed to stabilize the temperature here on Earth. Spohn explains, &ldquoplate tectonics is known to recycle carbon that is washed out of the atmosphere and digested by bacteria in the soil into the interior of the planet from where it can be outcast through volcanic activity. Now, if you have a planet without plate tectonics, you may have parts of this cycle, but it is broken because you do not have the recycling link.&rdquo

It has also been speculated that the lack of tectonic action on Venus contributed to its runaway greenhouse effect, which resulted in the immense temperatures it has today.

All this evidence adds up to paint a convincing picture of many lifeforms only surviving on worlds where plate tectonics are active. For astrobiologists, there is another interesting element to this story. Many within the planetary science community believe that to have plate tectonics, the near-surface rock must be weakened. The molecule most effective at doing this is H2O — water.

Raising hopes

So worlds with plate tectonics are likely to have water as well, which means they feature two ingredients theoretically necessary for life. This presents an exciting option: searching for plate tectonics on distant worlds as a sign of life. Spohn agrees that this is a possibility, but remains level-headed. &ldquoIt&rsquos an interesting idea, but is just speculation at the moment,&rdquo he explains. &ldquoAs a biosignature it would be very difficult to detect, especially with current technology&rdquo.

The problem is how challenging it is to spot plate tectonics from orbit even on our own Earth. The jig-saw puzzle shape of continents along with the presence of mountain belts provides indirect evidence. Mid-oceanic ridges are more convincing, but these are covered with water and not visible from space. To see features on an extrasolar planet would require a probe in orbit, and this is far beyond our technological ability. Even if we were able to achieve this, the evidence would still be indirect. Currently there is no conclusive way of remotely determining tectonic action on a planet.

So perhaps using these markers as an indication of life on other worlds is a step too far but as our technology becomes ever more complex it could become a possibility in the future. Imagine detecting an Earth-sized planet with an atmosphere, water, organic materials, and plate tectonics. It would unquestionably raise hopes for finding life in the universe.

Scientists believe there’s other life in the universe. Why haven’t we found it yet?

So says Geoffrey Marcy, an astronomer at the University of California at Berkeley and a participant in Stephen Hawking’s $100 million search for alien life, announced on Monday.

Marcy isn’t the only person who thinks so. Frank Drake, chairman emeritus of the Search for Extraterrestrial Intelligence Institute, came up with an equation in 1961 for calculating the abundance of alien civilizations capable of communicating with us.

When he plugs modern data into the formula, the number he comes up with is 10,000. And that just includes the ones he thinks we can detect, once we have the right tools searching the right places. Researchers examining data from NASA’s Kepler space telescope (including Marcy) announced in 2013 that they believe the Milky Way may harbor billions of planets that bear liquid water — a substance integral to the emergence of living things.

But if the universe is so full of the ingredients for alien life, why haven’t we found any yet? Or, more pertinently, considering how young humans are (100,000 years) compared to the age of the universe (13.8 billion years), why haven’t any aliens found us?

This question is known as the Fermi paradox, named for Italian physicist Enrico Fermi. According to scientific lore, Fermi was sitting around chatting about extraterrestrial life with fellow researchers (you know, as one does) when he asked, “So? Where is everybody?”

In the words of a University of Oregon professor’s lecture on the subject, Fermi reasoned that any civilization with “a modest amount of rocket technology and an immodest amount of imperial incentive” could colonize the galaxy by building artificially intelligent robotic probes that would self-reproduce as they journeyed beyond their home planet. While the distances between habitable planets are much too vast to be traversed in a lifetime, the theoretical robots have had millions or even billions of years to make the journey.

So far, notwithstanding the arguments of Roswell conspiracy theorists, we’ve seen no evidence of those probes. SETI experiments searching for radio signals or other broadcasts from possible alien civilizations have turned up empty.

There are three broad categories of explanations for Fermi’s paradox, each of which contains several of what you might call a “sub” explanation. Those range from reasonable — intelligent life is sending out signals, we just don’t know how to listen — to seemingly absurd — Earth is just a “zoo” built by aliens to hold us for their entertainment. Some come from astronomers and biologists, other from philosophers and economists. Still others seem to have more in common with science fiction than science. All of them are entertaining to think about, at least in the abstract sense.

22 stunning photos of our solar system and beyond in 2016

1. We really are alone.

This could be true for any number of reasons.

Life, as scientists have learned from repeated attempts to do so in a lab, is difficult to start from scratch. It requires a spontaneous sequence of events that somehow animates simple, non-living organic compounds and organizes them into more complex molecules capable of self-replication. So far, that’s only been known to happen once — when life on Earth began.

It’s possible that habitable planets like Earth are rarer than we think. Even if there are billions in the “Goldilocks zone” situated at the appropriate distance from their suns, maybe gamma rays or asteroid bombardment or other dangers from space prevented life from developing.

In a 1998 essay, George Mason economics professor Robin Hanson proposed the idea of a “great filter” — something “along the path between simple dead stuff and explosive life” that is very difficult or even impossible to move beyond. If the “filter” is somewhere in the early days of life’s beginnings, that would explain why no other planet has proven capable of nurturing life.

The notion that we’re unique in the universe is what paleontologist Peter Ward and astronomer Donald Brownlee call the rare Earth hypothesis. They argue that the presence of complex life on this planet may be a once-in-a-Big-Bang occurrence.

Earthlings may have to resign themselves to the fact that we’re on our own.

2. Life is out there we just haven’t heard from it.

That said, there’s good reason to believe that life on Earth is not unique.

First of all, we’re pretty sure that water — that essential indicator of conditions for life — is fairly ubiquitous. NASA believes that there are large quantities of water in the atmospheres of at least four other planets in our solar system and ice on countless other celestial bodies. And in April, researchers announced in the journal Nature that they’d found the first evidence of organic molecules in an infant star system.

But if we do have otherworldly company, researchers like Marcy (one of the brains tapped for Hawking’s $100 million search) want to know why we haven’t heard from them.

“The absence of strong radio beacons, television broadcasts, robotic spacecraft, obelisks on the moon — all of those absences add up to give us the suggestion that our galaxy is not teeming with technological life,” Marcy told The Washington Post in February.

Which brings us to sub-explanation number one: The other life that exists isn’t capable of reaching out. This is a popular one.

Earlier this year, NASA’s chief scientist Ellen Stofan boldly predicted that we would find indications of life beyond Earth in the next 10 to 20 years. But what we find won’t be “little green men,” she cautioned at a public panel in April.

“We are talking about little microbes,” she said, according to the Los Angeles Times.

Another sub-explanation is that they are communicating, but either their signals haven’t reached us or they have and we don’t know how to recognize them.

Maybe, as astronomer Carl Sagan once pointed out, human brains don’t work at the right speed to comprehend an alien message — perhaps they work at a much faster pace than us, and their signals are gone in a blip, or maybe they are much, much slower, and their messages arrive at too sluggish a pace to be perceived as anything other than white noise. Or, as theoretical physicist Michio Kaku has proposed, super-intelligent aliens are out there and our brains are just too primitive to perceive them as such.

A third is that previous intelligent civilizations came and went before humans even arrived on the scene. They may have been annihilated by overpopulation or nuclear warfare or dangerous experiments or deadly disease or any number of other horrifying catastrophes. Any of these would suggest that Hanson’s great filter isn’t somewhere in our past, but rather in our future — that most civilizations destroy themselves eventually and we’re inexorably heading toward our doom.

This, as Oxford University philosopher Nick Bostrom has pointed out, is a chilling scenario, and perhaps a reason to hope that Hawking’s search doesn’t turn up remnants of any ancient alien civilizations.

“The silence of the night sky is golden,” Bostrom wrote.

A fourth proposal is that intelligent life is out there it’s just smart enough to stay silent.

Humans have been cavalierly sending signals into space since before we launched the Golden Record on board the Voyager spacecraft in 1977, but it’s possible that’s a dangerous game to play. Perhaps there are vicious predator civilizations out there eager to feed on naive, idiotic species like ourselves, or even one super-advanced civilization that exterminates all competitors once they reach a certain level of intelligence. This is why many scientists — including Sagan, who orchestrated the Golden Record project — have advised against “active SETI,” or sending messages out into the unknown.

“ETI’s [extraterrestrial intelligence] reaction to a message from Earth cannot presently be known,” reads a petition signed by 28 prominent scientists and thought leaders, including Marcy and SpaceX founder Elon Musk. “We know nothing of ETI’s intentions and capabilities, and it is impossible to predict whether ETI will be benign or hostile.”

Scientists Believe Humans Will One Day Colonize the Universe

Hubble Deep Field image showing myriad galaxies dating back to the beginning of time. Image by Robert Williams and the Hubble Deep Field Team (STScI) and NASA.

A new study from the University of Oxford looks at the possibility of human colonization throughout the universe.

Scientists as eminent as Stephen Hawking and Carl Sagan have long believed that humans will one day colonize the universe. But how easy would it be, why would we want to, and why haven’t we seen any evidence of other life forms making their own bids for universal domination?

A new paper by Dr Stuart Armstrong and Dr Anders Sandberg from Oxford University’s Future of Humanity Institute (FHI) attempts to answer these questions. To be published in the August/September edition of the journal Acta Astronautica, the paper takes as its starting point the Fermi paradox – the discrepancy between the likelihood of intelligent alien life existing and the absence of observational evidence for such an existence.

Dr Armstrong says: “There are two ways of looking at our paper. The first is as a study of our future – humanity could at some point colonize the universe. The second relates to potential alien species – by showing the relative ease of crossing between galaxies, it makes the lack of evidence for other intelligent life even more puzzling. This worsens the Fermi paradox.”

The paradox, named after the physicist Enrico Fermi, is something of particular interest to the academics at the FHI – a multidisciplinary research unit that enables leading intellects to bring the tools of mathematics, philosophy and science to bear on big-picture questions about humanity and its prospects.

Dr Sandberg explains: “Why would the FHI care about the Fermi paradox? Well, the silence in the sky is telling us something about the kind of intelligence in the universe. Space isn’t full of little green men, and that could tell us a number of things about other intelligent life – it could be very rare, it could be hiding, or it could die out relatively easily. Of course it could also mean it doesn’t exist. If humanity is alone in the universe then we have an enormous moral responsibility. As the only intelligence, or perhaps the only conscious minds, we could decide the fate of the entire universe.”

According to Dr Armstrong, one possible explanation for the Fermi paradox is that life destroys itself before it can spread. “That would mean we are at a higher risk than we might have thought,” he says. “That’s a concern for the future of humanity.”

Dr Sandberg adds: “Almost any answer to the Fermi paradox gives rise to something uncomfortable. There is also the theory that a lot of planets are at roughly at the same stage – what we call synchronized – in terms of their ability to explore the universe, but personally I don’t think that’s likely.”

As Dr Armstrong points out, there are Earth-like planets much older than the Earth – in fact most of them are, in many cases by billions of years.

Dr Sandberg says: “In the early 1990s we thought that perhaps there weren’t many planets out there, but now we know that the universe is teeming with planets. We have more planets than we would ever have expected.”

A lack of planets where life could evolve is, therefore, unlikely to be a factor in preventing alien civilizations. Similarly, recent research has shown that life may be hardier than previously thought, weakening further the idea that the emergence of life or intelligence is the limiting factor. But at the same time – and worryingly for those studying the future of humanity – this increases the probability that intelligent life doesn’t last long.

The Acta Astronautica paper looks at just how far and wide a civilization like humanity could theoretically spread across the universe. Past studies of the Fermi paradox have mainly looked at spreading inside the Milky Way. However, this paper looks at more ambitious expansion.

Dr Sandberg says: “If we wanted to go to a really remote galaxy to colonize one of these planets, under normal circumstances we would have to send rockets able to decelerate on arrival. But with the universe constantly expanding, the galaxies are moving further and further away, which makes the calculations rather tricky. What we did in the paper was combine a number of mathematical and physical tools to address this issue.”

Dr Armstrong and Dr Sandberg show in the paper that, given certain technological assumptions (such as advanced automation or basic artificial intelligence, capable of self-replication), it would be feasible to construct a Dyson sphere, which would capture the energy of the sun and power a wave of intergalactic colonization. The process could be initiated on a surprisingly short timescale.

But why would a civilization want to expand its horizons to other galaxies? Dr Armstrong says: “One reason for expansion could be that a sub-group wants to do it because it is being oppressed or it is ideologically committed to expansion. In that case you have the problem of the central civilization, which may want to prevent this type of expansion. The best way of doing that get there first. Pre-emption is perhaps the best reason for expansion.”

Dr Sandberg adds: “Say a race of slimy space aliens wants to turn the universe into parking lots or advertising space – other species might want to stop that. There could be lots of good reasons for any species to want to expand, even if they don’t actually care about colonizing or owning the universe.”

He concludes: “Our key point is that if any civilization anywhere in the past had wanted to expand, they would have been able to reach an enormous portion of the universe. That makes the Fermi question tougher – by a factor of billions. If intelligent life is rare, it needs to be much rarer than just one civilization per galaxy. If advanced civilizations all refrain from colonizing, this trend must be so strong that not a single one across billions of galaxies and billions of years chose to do it. And so on.”

“We still don’t know what the answer is, but we know it’s more radical than previously expected.”

Drinking seawater

You might be surprised to find out that it’s not the essentials - such as water running out - that threatens human life on earth. In fact, Dr. Armstrong explains that: “We could have enough food, water and energy for the whole human race for the foreseeable future and at reasonable costs. Take water… most of the world’s water is seawater. The worst thing we’d have to do is get all our water from the sea! But there’s plenty of it. We’d have to remove the salt to make it drinkable [in a process known as desalination] but this is feasible”.

“Now let’s look at food. The ultimate way of producing food would be by growing plants in greenhouses without soil - this is called hydroponic growing. We’d use much less water growing food this way which would lead to a huge decrease in water use,” he says.

Cloudy, with a Chance of Habitability

Some researchers call K2-18 b and its ilk &ldquosuper Earths&rdquo others prefer to call them &ldquomini Neptunes.&rdquo But regardless of nomenclature, the most obvious fact about these objects is that none of them orbit our sun, despite being the most plentiful planetary type in the Milky Way. All we can really know of them currently comes from extrasolar studies. And so far, those studies show that most of these planets, somewhere in size between Earth and Neptune, are not very much like Earth at all.

&ldquoI like to call them &lsquohybrid&rsquo planets, these worlds with rocky cores and thick hydrogen envelopes,&rdquo Benneke says. &ldquoThis is not a bare rock with a thin atmosphere like Earth, but this is also not a giant planet like Neptune or Jupiter.&rdquo

One appeal of studying such intermediate worlds&mdashmany more of which are already being uncovered by the ongoing TESS mission&mdashis the possibility they will reveal something fundamental about how planets of all sizes come to be.

&ldquoWe think that for planets somewhere around 1.8 times the size of Earth, there is a transition from rocky to gaseous worlds that takes place,&rdquo says Laura Kreidberg, an astronomer at the Center for Astrophysics at Harvard University and the Smithsonian Institution (CfA), who did not take part in the studies. &ldquoK2-18 b is close to that border, so [these studies] are giving us our first glimpse into the atmosphere of a world near this transition.&rdquo

Nikole Lewis, an astronomer at Cornell University, who was not involved in either paper, notes that this is not the first time signs of water vapor, clouds and perhaps even rain have been seen on worlds outside the solar system. But those earlier discoveries have come from K2-18 b&rsquos larger, hotter cousins around other stars, worlds that are more firmly on the &ldquoNeptune&rdquo side of the planetary divide. &ldquoK2-18 b represents a great step on the path to probing cooler and smaller planets,&rdquo she says. &ldquoIt has the potential to inform us about how atmospheres form and evolve for planets at or near the habitable zone around red dwarf stars, which will be important for understanding the potential habitability of smaller &lsquoEarth-sized&rsquo planets.&rdquo

Most importantly, water vapor on K2-18 b would be the best evidence yet that small planets in the habitable zones of red dwarfs can possess atmospheres at all. In some respects, diminutive red dwarfs can punch well above their weight, emitting atmosphere-eroding amounts of radiation that peak early in the stars&rsquo lives just when newborn planets may be most vulnerable. And the handful of earlier Hubble studies of tiny, close-in red dwarf worlds have been discouraging: Attempts to study the putative atmospheres of several potentially habitable planets transiting an ultradim red dwarf called TRAPPIST-1 provided inconclusive results. And a more recent probe of LHS 3844 b, a transiting red dwarf world a third larger in size than our own, suggested that planet may well have no air at all.

&ldquoThe vast majority of the habitable space in the universe may be around red dwarfs, because these are the most common stars, and they happen to have lots of rocky planets really close to them,&rdquo says Nicolas Cowan, an astronomer at McGill University, who is unaffiliated with either of the new papers. &ldquoAfter the study showing LHS 3844 b looks like a dry, barren rock, some of us started getting worried. Maybe red dwarf worlds would turn out to be red herrings for astrobiology.&rdquo

That concern is why K2-18 b is &ldquoa huge deal,&rdquo Cowan says, despite its distinctly unearthly and somewhat unhospitable state. &ldquoIt suggests the most common planetary real estate in the universe can also be habitable&mdashnot only with atmospheres but with water vapor, too.&rdquo

Even so, not everyone is convinced the claims of water vapor are much more than hot air. &ldquoThe statistical significance of the claimed detection is not strong,&rdquo says David Charbonneau, an astronomer at CfA, who co-discovered the first transiting planet back in 1999. Unlike that finding, which was based on two distinct data sets, the new discovery that was shared between two teams relies on just one&mdashfrom Hubble, which was never designed to perform such delicate, challenging measurements. &ldquoYes, it is suggestive,&rdquo Charbonneau says. &ldquoBut astronomers have been studying transiting planets for 20 years, so I think we are well past the epoch of &lsquosuggestive&rsquo studies.&rdquo

Is there life on other planets and if so how frequent? - Biology

Is there really life on Mars? Was there once cellular material on the red planet? Scientists have been studying these questions for a long time, and now they have some new information that may give some clues. Scientifically speaking, to study the controversy about life on Mars, it is important to understand what the work of scientists is all about. How do scientists develop a theory like life exists on Mars?

The easiest way to test the theory of life on Mars is to create a series of predictions that can be tested experimentally. If the tests support the predictions, then the theory will gain support if the tests are inconclusive or do not support the predictions, then the theories will lose support.

Two of the essential scientific questions are what is life, really, and how did it begin? Scientists predict that on primitive Earth, the atmosphere consisted mostly of ammonia, water vapor, methane, and hydrogen. With exposure to intense heat, ultraviolet light, electrical storms, and other conditions, organic molecules conbined to form membrane-bound droplets call coacervates. These may have been the precursors of the first living cells on Earth. If Mars could support life in its early history, then life probably formed on many other planets, too.

One period in class to complete the analysis of the Mars evidence scenario. Homework time to write a report describing the research plan. One period in class to make and observe coacervates.

Watch the video: Top 10 Πλανητες Που Πιθανόν Να Φιλοξενούν Ζωή (November 2022).