How to detect life on exoplanets? The answer is very original, life is reflected on the Moon. The light of life has a special feature, a biosignature, if observed indirectly, reflected from a nearby aster. There is life on Earth, and it shows from the Moon. The concept is revealed in the journal Nature on March 1, 2012, by a team of astrophysicists who used the VLT of the European Southern Observatory, located in the Atacama Desert in the Chilean Andes. Yes, traces of life on Earth are printed on the earthshine from the Moon. "The sun illuminates the Earth and the light reflects off the surface of the moon. The lunar surface acts as a giant mirror and reflects from us the light of the Earth - and that is what we observed with the VLT, "says Michael Sterzik (ESO), lead author of the scientific paper. Rather than measuring the light intensity of the reflected light, scientists have focused their attention on the polarization of light. By analyzing the faint light of terrestrial radiation on the moon, they found evidence of the existence of organic life.
Stefano Bagnulo, coauthor of the study, explains the concept: "the light of a distant exoplanet is largely lost in the glare of its star, it is therefore difficult to analyze. It's a bit like trying to study a speck of dust next to a powerful light bulb. The light reflected by a planet is polarized, while that of the star is not. So, polarimetry techniques help us to distinguish the faint light reflected from an exoplanet, in the dazzling light of a star. "Spectropolarimetry can help us measure the polarization of the reflected light to reconstruct the material content of the exoplanet.
nota: the earthshine is sunlight reflected from the Earth and illuminates the moon very weakly. When the Moon appears as a thin crescent in the twilight sky from Earth, it is often possible to see the rest of the lunar disk is faintly luminous. This light, called, earthshine, is caused by sunlight reflecting off Earth and illuminating the lunar surface.
What biosignatures (life indicators), which will reveal the presence of life on distant exoplanets? How to find oxygen, ozone, methane, carbon dioxide and other gases? When light is polarized, its electric field components and magnetic field have a specific orientation. In the not polarized light, the orientation is random fields and has no preferred direction. To measure the polarization scientists used a special mode of FORS2 instrument on the Very Large Telescope (VLT). They were able to deduce, from observations that the Earth's atmosphere is partly cloudy, a portion of its surface is covered by oceans and vegetation there is.
Enric Palle (Instituto de Astrofísica de Canarias, Tenerife, Spain): "Finding life outside the solar system depends on two things, first of all that life exists elsewhere, and if this is the case, having the ability technique to detect." "This work constitutes an important step towards the acquisition of this capability. Ultimately, spectropolarimetry, seeking processes of photosynthesis, can tell us if life, vegetative form, emerged somewhere in the Universe,", concludes Michael Sterzik.
Nota: The next generation of telescopes, and especially the E-ELT (European Extremely Large Telescope), will have the ability to use this technique to study the distant exoplanets.
Subtle traces of life
On 3 December 2013 the powerful Hubble Space Telescope NASA saw the subtle traces of water on alien worlds. Two teams of scientists have found weak signatures of water in foggy atmospheres five distant planets. The five planets are hot Jupiters, massive worlds orbiting close around their host stars. The presence of water in the atmosphere, has been previously reported on some exoplanets orbiting stars beyond our solar system. However this is the first study to measure conclusively, by comparing the profiles and intensities of these signatures on several worlds. The five planets studied are WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b, all they orbit close to their star. Of course, the signal strength of their signatures of water varies depending on their atmosphere. For example, WASP-17b is a planet with a particularly dense atmosphere, while HD209458b has the strongest signals. Signatures for the other three planets, WASP-12b, WASP-19b and XO-1b, are also compatible with the presence of water. « We're very confident that we see a water signature for multiple planets, » said Avi Mandell, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and lead author of an Astrophysical Journal paper, published today, describing the findings for WASP-12b, WASP-17b and WASP-19b. Both teams used the camera 3 to Hubble's Wide Field to explore the details of the absorption of light through the atmospheres of planets. Observations were made in different wavelength range of the infrared where the water signature, if present, would appear. The teams have compared these planets, forms and intensities of absorption profiles and coherence signatures of water. These exceptionally difficult studies, may be made only if the planets are identified when they pass in front of their star. Researchers can identify gases in the atmosphere of a planet by determining the wavelength of the light from the star that are transmitted and those that are partially absorbed lengths.
Image: This NASA video explains how researchers are studying the characteristics of exoplanets, especially the size and atmospheric composition. Exoplanets are too distant to be seen directly, but through the light absorbed by passing in transit to their star, scientists can infer by indirect methods, many hidden features such as mass, density, composition (rocky or gaseous ), the depth of its atmosphere. All this information is encrypted while in transit in the color of the light absorbed. Each wavelength absorbed in the light spectrum reveals a distinct molecular chemical footprint. Which most interested researchers are signs of life such as water vapor (H2O), oxygen (O2) and methane (CH4).
Life on Earth, in fast
About 500 million years after the birth of the Earth, bacteria appear, are simple cells without nucleus (prokaryotes), and will evolve for 1.5 billion years until eukaryotic bacteria with a core 2 billion years after the birth of the Earth, the expected occasion is and multicellular organisms appear. Complexity will then accelerate its walking in front, even 100 million years to see shellfish, and crustaceans. Another 100 million years and the fish appear. This is the time when the Earth becomes a haven for plants and forests. The atmosphere will be significantly altered because photosynthesis will produce oxygen and ozone, protectors of the sun's harmful rays. Living organisms do not need to stay safe in the ocean, life is going to try and pass out water to invade the land.
There are 200 million years, birds and reptiles make their appearance, 50 million years later it was the turn of the dinosaurs. There are 100 million years, mammals invade the earth. There are 20 to 30 million years are the primates who show their teeth and there are about 6 million years, the lineage of Homo sapiens entered the earthly scene. It took the universe, invent galaxies, stars, planets, oceans and atmospheres, under skies still more conducive to achieve the complexity observable today. From the void, to civilized man, where the top of this complexity frantic, knowing that it remains the germs the life, eternity?