astrobiology – It's Interesting

Solar Flare

The Earth will stay livable for another 1.75 to 3.25 billion years before ”a catastrophic and terminal extinction event for all life,” according to a new study.

After that, the planet will be in the Sun’s “hot zone” — meaning surface water would “evaporate.”

The study was published in the journal Astrobiology by astrobiologists at the University of East Anglia.

“We used stellar evolution models to estimate the end of a planet’s habitable lifetime by determining when it will no longer be in the habitable zone. We estimate that Earth will cease to be habitable somewhere between 1.75 and 3.25 billion years from now,” Andrew Rushby, from UEA’s school of Environmental Sciences and the leader of the research said on the UEA website. ”After this point, Earth will be in the ‘hot zone’ of the sun, with temperatures so high that the seas would evaporate. We would see a catastrophic and terminal extinction event for all life.

And life doesn’t necessarily mean humans — it can mean things as simple as micro-organisms.

“Of course conditions for humans and other complex life will become impossible much sooner — and this is being accelerated by anthropogenic climate change,” Rushby wrote. “Humans would be in trouble with even a small increase in temperature, and near the end only microbes in niche environments would be able to endure the heat.”

Rushby said that the most important part of figuring out the total habitable time for a planet is that it gives an idea of how long it takes for complex life to develop.

“Looking back a similar amount of time, we know that there was cellular life on earth. We had insects 400 million years ago, dinosaurs 300 million years ago and flowering plants 130 million years ago. Anatomically modern humans have only been around for the last 200,000 years — so you can see it takes a really long time for intelligent life to develop,” he wrote on his school site. “The amount of habitable time on a planet is very important because it tells us about the potential for the evolution of complex life — which is likely to require a longer period of habitable conditions.”

.
AP Photo/NASAThe Earth will stay livable for another 1.75 to 3.25 billion years before “a catastrophic and terminal extinction event for all life,” according to a new study.
TwitterGoogle+ LinkedIn Email CommentsMore
TumblrPinterestRedditDiggFarkItStumbleUpon
.The Earth will stay livable for another 1.75 to 3.25 billion years before ”a catastrophic and terminal extinction event for all life,” according to a new study.

After that, the planet will be in the Sun’s “hot zone” — meaning surface water would “evaporate.”

The study was published in the journal Astrobiology by astrobiologists at the University of East Anglia.

And life doesn’t necessarily mean humans — it can mean things as simple as micro-organisms.

Related
Two new planets are the closest NASA has come so far to finding another like Earth
More planets, more possible life: Discovery of planet around Alpha Centauri will accelerate search for E.T.
All humans may be ‘Martians’: Growing evidence that all life on Earth came ‘on a rock’ from Mars
Famed SETI astronomer retiring, says discovery of alien life ‘very close’
Memo on puported UFO discovery in New Mexico becomes most read file in FBI’s electronic reading room
.“Of course conditions for humans and other complex life will become impossible much sooner — and this is being accelerated by anthropogenic climate change,” Rushby wrote. “Humans would be in trouble with even a small increase in temperature, and near the end only microbes in niche environments would be able to endure the heat.”

Rushby said that the most important part of figuring out the total habitable time for a planet is that it gives an idea of how long it takes for complex life to develop.

.This, in turn, can help us search for how complex life would develop on other planets. Scientists are looking for an Earth-size planet that’s in the habitable zone or the so-called “Goldilocks” zone — that sweet spot that’s not too hot and not too cold where water, which is essential for life as know it, could exist on the surface.

“Looking at habitability metrics is useful because it allows us to investigate the potential for other planets to host life, and understand the stage that life may be at elsewhere in the galaxy.”

The Earth is actually near the outer edge of the habitable zone. Scientists say that it would be much more likely for complex life to exist on planets that are closer to the sun than us than further from it, though the strip of “Goldilocks” space, in intrastellar terms, is quite small.

“Interestingly, not many other predictions based on the habitable zone alone were available, which is why we decided to work on a method for this. Other scientists have used complex models to make estimates for the Earth alone, but these are not suitable for applying to other planets,” Rushby wrote.

In April, NASA unveiled new planetary results from its Kepler mission, showing two very Earth-like planets.

“Two of the newly discovered planets orbit a star smaller and cooler than the sun. Kepler-62f is only 40% larger than Earth, making it the exoplanet closest to the size of our planet known in the habitable zone of another star,” NASA explains in a release. “Kepler-62f is likely to have a rocky composition. Kepler-62e orbits on the inner edge of the habitable zone and is roughly 60% larger than Earth.”

The distant duo are the best candidates for habitable planets that astronomers have found so far, said William Borucki, the chief scientist for NASA’s Kepler telescope. Both are Earth-sized and in the habitable zone.

Another key planet, Kepler 22b, was unveiled on December 5, 2011. It’s 2.4 times the size of the Earth, orbiting a Sun-like star every 290 days. Another, Gliese 581d, was discovered around the same time.

“One of the planets that we applied our model to is Kepler 22b, which has a habitable lifetime of 4.3 to 6.1 billion years. Even more surprising is Gliese 581d which has a massive habitable lifetime of between 42.4 to 54.7 billion years. This planet may be warm and pleasant for 10 times the entire time that our solar system has existed!” Rushby wrote.

The planets were discovered by NASA’s Kepler space telescope, which measures fluctuations in the brightness of more than 150,000 stars in order to detect planets. Scientists then used ground-based telescopes to peer at the information the spacecraft has gathered in order to analyze and verify its discoveries.

However, none of the discovered planets are perfect Earth analogues, Rusby wrote.

“To date, no true Earth analogue planet has been detected. But it is possible that there will be a habitable, Earth-like planet within 10 light-years, which is very close in astronomical terms. However reaching it would take hundreds of thousands of years with our current technology.”

He says that the best bet to transplant the human race remains right next door. On Mars.

“If we ever needed to move to another planet, Mars is probably our best bet. It’s very close and will remain in the habitable zone until the end of the Sun’s lifetime — six billion years from now.”

http://news.nationalpost.com/2013/09/19/life-on-earth-will-be-obliterated-by-the-heat-of-the-sun-1-75-to-3-25-billion-years-from-now/

Polonnaruwa%20meteorite

On 29 December 2012, a fireball lit up the early evening skies over the Sri Lankan province of Polonnaruwa. Hot, sparkling fragments of the fireball rained down across the countryside and witnesses reported the strong odour of tar or asphalt.

Over the next few days, the local police gathered numerous examples of these stones and sent them to the Sri Lankan Medical Research Institute of the Ministry of Health in Colombo. After noticing curious features inside these stones, officials forwarded the samples to a team of astrobiologists at Cardiff University in the UK for further analysis.

The results of these tests, which the Cardiff team reveal today, are extraordinary. They say the stones contain fossilised biological structures fused into the rock matrix and that their tests clearly rule out the possibility of terrestrial contamination.

In total, Jamie Wallis at Cardiff University and a few buddies received 628 stone fragments collected from rice fields in the region. However, they were able to clearly identify only three as possible meteorites.

The general properties of these three stones immediately mark them out as unusual. One stone, for example, had a density of less than 1 gram per cubic centimetre, less than all known carbonaceous meteorites. It had a partially fused crust, good evidence of atmospheric heating, a carbon content of up to 4 per cent and contained an abundance of organic compounds with a high molecular weight, which is not unknown in meteorites. On this evidence, Wallis and co think the fireball was probably a small comet.

The most startling claims, however, are based on electron microscope images of structures within the stones (see above). Wallis and co say that one image shows a complex, thick-walled, carbon-rich microfossil about 100 micrometres across that bares similarities with a group of largely extinct marine dinoflagellate algae.

They say another image shows well-preserved flagella that are 2 micrometres in diameter and 100 micrometres long. By terrestrial standards, that’s extremely long and thin, which Wallis and co interpret as evidence of formation in a low-gravity, low-pressure environment.

Wallis and co also measured the abundance of various elements in the samples to determine their origin. They say that low levels of nitrogen in particular rule out the possibility of contamination by modern organisms which would have a much higher nitrogen content. The fact that these samples are also buried within the rock matrix is further evidence, they say.

Wallis and co are convinced that the lines of evidence they have gathered are powerful and persuasive. “This provides clear and convincing evidence that these obviously ancient remains of extinct marine algae found embedded in the Polonnaruwa meteorite are indigenous to the stones and not the result of post-arrival microbial contaminants,” they conclude.

There’s no question that a claim of this kind is likely to generate controversy. Critics have already pointed out that the stones could have been formed by lightning strikes on Earth although Wallis and co counter by saying there was no evidence of lightning at the time of the fireball and that in any case, the stones do not bear the usual characteristics of this kind of strike. What’s more, the temperatures generated by lightning would have destroyed any biological content.

Nevertheless, extraordinary claims require extraordinary evidence and Wallis and co will need to make their samples and evidence available to the scientific community for further study before the claims will be taken seriously.

If the paper is taken at face value, one obvious question that arises is where these samples came from. Wallis and co have their own ideas: “The presence of fossilized biological structures provides compelling evidence in support of the theory of cometary panspermia first proposed over thirty years ago,” they say.

This is an idea put forward by Fred Hoyle and Chandra Wickramasinghe, the latter being a member of the team who has carried out this analysis.

There are other explanations, of course. One is that the fireball was of terrestrial origin, a remnant of one of the many asteroid impacts in Earth’s history that that have ejected billions of tonnes of rock and water into space, presumably with biological material inside. Another is that the structures are not biological and have a different explanation.

Either way, considerably more work will have to be done before the claims from this team can be broadly accepted. Exciting times ahead!

http://www.technologyreview.com/view/512381/astrobiologists-find-ancient-fossils-in-fireball-fragments/

Thanks to Kebmodee for bringing this to the attention of the It’s Interesting community.

It's Interesting

Category: astrobiology

Life on Earth will be obliterated by the heat of the sun (1.75 to 3.25 billion years from now)

Astrobiologists Find Ancient Fossils in Fireball Fragments