44 trillion watts of Earth’s heat

  

Some 44 trillion watts of heat continually flow from Earth's interior into space. Where does this come from?

One trillion is 1,000 billion. So 44 terawatts works out to 44,000 billion watts. And how did geologists come by the staggering figure? They relied on temperature measurements from more than 20,000 boreholes around the world.

Radioactive decay of uranium, thorium, and potassium in earth's crust and mantle is a principal source of this heat, reports the journal Nature Geoscience.

In 2005, scientists in the Japan-based KamLAND (Kamioka Liquid-scintillator Antineutrino Detector) collaboration first showed that there was a way to measure the contribution directly. 

A neutrino, more similar to an electron, is an elementary particle that travels close to the speed of light, but unlike electrons, doesn't carry an electric charge, according to a statement by Berkeley Lab, which is a major contributor to KamLAND. 

The trick was to catch what KamLAND dubbed geoneutrinos -- more precisely, geo-antineutrinos -- emitted when radioactive isotopes (same chemical element with different masses) decay.

"As a detector of geoneutrinos, KamLAND has distinct advantages," says Stuart Freedman, member of US Department of Energy's Berkeley Lab. 

Freedman, also professor in physics at the University of California, Berkeley, said: "KamLAND was specifically designed to study antineutrinos. We are able to discriminate them from background noise and detect them with very high sensitivity." 

One thing that's at least 97 per cent certain is that radioactive decay supplies only about half the earth's heat. Other sources - primordial heat left over from the planet's formation, and possibly others as well - must account for the rest. 

Antineutrinos are produced not only in the decay of uranium, thorium, and potassium isotopes but in a variety of others, including fission products in nuclear power reactors.

Newly found super-Earth could be a water world

A 'super-Earth' discovered recently some 40 light years away could be covered with either water vapour or a thick haze, scientists have said.

The planet, which is 2.6 times bigger than Earth, has given scientists their first chance to analyse the atmosphere of a world outside the solar system.

A team of astronomers who used the European Southern Observatory's 3.6m telescope in Chile to analyse the planet's atmosphere said they have found possible evidence of water in the form of steam shrouding the planet.

Alternatively, the planet, which is orbiting a star in the constellation of Ophiuchus, could have a mostly hydrogen atmosphere hidden beneath high clouds or hazes, as seen on Venus or Saturn's moon Titan, they said.

Codenamed GJ 1214b, the planet hugs its parent star at a distance of only two million kilometres - 70 times closer than the Earth is to the Sun, the Daily Mail reported.

That's why conditions on its surface are hot, said the astronomers who carried out their study by analysing light coming from the star as the planet passed in front of it. The planet travels across the disc of its parent star

once every 38 hours as it orbits.

Specific wavelengths of the starlight were absorbed by gases in the atmosphere, providing clues to its composition.

Before making the observations, scientists had predicted a steam atmosphere, a cloud-obscured hydrogen atmosphere, or a deep hydrogen-rich atmosphere like that of Neptune. But the measurements did not show tell-tale signs of hydrogen, thereby ruling out the third option.

Dr Jacob Bean, from the Harvard-Smithsonian Centre for Astrophysics in Massachusetts, who led the research team, said: "This is the first super-Earth to have its atmosphere analysed. We've reached a real milestone on the road toward characterising these worlds.

"Although we can't yet say exactly what that atmosphere is made of, it is an exciting step forward to be able to narrow down the options for such a distant world to either steamy or hazy. Follow-up observations in longer wavelength infrared light are now needed to determine which of these atmospheres exists Newly found super-Earth could be a waterworld: scientists on GJ 1214b."

The number of confirmed exoplanets reached 500 last month and more have been confirmed since. The findings were published in the journal Nature.