MessageToEagle.com - In recent years, astronomers have detected hundreds of extrasolar planets.
Many of these
exoplanets lie within habitable zones, the zones around their stars warm enough for liquid water to persist on a planet's
surface, raising hopes that life as we know it might live on these distant worlds.
Ground-based observatories and proposed-but-cancelled spacecraft such as the European Space Agency's Darwin project
or NASA's Terrestrial Planet Finder could scan the atmospheres of exoplanets for signs of extraterrestrial life.
Molecules each absorb specific types of light, resulting in patterns known as spectra that allow scientists to identify
what the molecules are.
Some chemicals or combinations of chemicals might be unique to life as we know it, and could thus
serve as strong evidence of aliens.
Carbonaceous chondrites are thought to be a potential source of early Earth’s volatile elements - including hydrogen,
nitrogen, and carbon - and possibly organic material. Artist concept Credit: NASA's Goddard Space Flight Center/Chris Smith
One key gas astrobiologists looking for extraterrestrial life would concentrate on would be oxygen, since researchers
often think this molecule is too chemically reactive to remain for long in the atmosphere of a rocky planet like Earth
without organisms to continuously produce it. Another possibility would be methane, a colorless, odorless, flammable
organic gas that microbes on Earth produce.
Seeing both together in an exoplanet's atmosphere might be an especially
significant sign of life, since they would both ordinarily remove each other from the atmosphere without something
like life to constantly replenish them.
For more than 40 years, hints of methane have been seen on Mars, the first organic compound seen there. In the last decade,
researchers have even suggested they have seen methane clouds that may have been forming over the red planet during the
summer months in the last decade, raising the possibility of past or even extant organisms just below the surface, although
these findings remain hotly contested.
Although life or the byproducts of life are responsible for nearly all the methane found in Earth's atmosphere, it is not
the only source of the gas. For instance, volcanism can produce methane, as can chemical reactions between water, carbon
dioxide and minerals.
Another potential source of methane are carbon-rich micrometeoroids that generate the gas as the compounds in them burn
up while entering a planet's atmosphere. Our solar system's main asteroid belt happens to be dominated by
Although the number of micrometeoroids hitting Mars would not explain the levels of methane seen there, exoplanets in
much dustier systems could potentially have enough methane produced in this manner to give off a false atmospheric
signature of life.
"This could pose a problem, since the search for life on these exoplanets is dependent on remote observations such as
spectroscopic analysis of their atmospheres, as had been used to detect the methane in the atmosphere of Mars," said
researcher Richard Court, a planetary geologist at Imperial College London. "There is no chance of spacecraft physically
visiting these exoplanets many light years away in the foreseeable future."
Click on image to enlarge
This image shows concentrations of methane discovered on Mars. Credit: NASA
Past research suggests the only systems likely to possess debris disks dense enough to mimic a methane signature of life
are either very young, or systems undergoing a massive set of collisions, such as was the case in our solar system during
the Late Heavy Bombardment about 3.9 billion years ago, when millions of rocks cataclysmically blasted Earth and the rest
of the inner solar system over a roughly 100-million-year period.
"Astronomers have been able to observe events analogous to the Late Heavy Bombardment occurring in other star systems,"
Deception in the Universe - Meteors can fool us to think alien worlds are inhabited with life.
To see how much methane carbonaceous micrometeoroids might generate on exoplanets, scientists calculated what an early,
dustier version of our solar system was like. Currently Earth receives about 40,000 metric tons of micrometeoroids annually,
while Mars sees about 12,000 metric tons. The researchers estimate that during the Late Heavy Bombardment, Earth and Mars
saw about 1,000 to 10,000 times more.
During the entire Late Heavy Bombardment, Earth may have received about 33 million
billion metric tons of micrometeoroids, while Mars received 1.7 million billion metric tons. This all may be enough for
an exoplanet to have enough methane to make it look as if it might have life.
"These are the first people to address exoplanet atmospheres as they relate to micrometeoroids that produce methane upon
atmospheric entry — people working with exoplanets hadn't thought of this before, and it's cool and something we should
be aware of," said planetary scientist Sara Seager at the Massachusetts Institute of Technology, who did not take part
in this study.
Click on image to enlarge
When an exoplanet passes in front of its star from our point of view, atoms in its atmosphere absorb
some of the starlight at specific wavelengths. These wavelengths form a unique fingerprint,
allowing scientists to identify the presence of specific gases in an exoplanet's atmosphere. Credit: European Space Agency,
with adaptations by David Sing
Court did caution that they assumed that the chemistry and abundance of the organic matter in micrometeorites falling
to Earth is similar to that of micrometeorites in other star systems.
"While some differences are inevitable, it is
likely to be a reasonable assumption, because a search for evidence of life on planets outside the solar system will
naturally seek to investigate a star system as similar as possible to ours," he said.
So far astronomers have detected a number of exoplanetary systems that may possess both planets and debris disks.
One example may include Gliese 581 about 20 light years from Earth, which has one and maybe two "super-Earths" — rocky
planets larger than our own that can reach up to 10 times Earth's mass — around the red dwarf of the system's habitable zone.
"As we observe more star systems, it will be possible to apply our work to more extrasolar planets," Court said.
Radio Emission From Ultracool Dwarf Detected By Arecibo Telescope
The Arecibo Telescope in Puerto Rico has discovered sporadic bursts of polarized radio emission from the T6.5 brown J1047+21.
Because Arecibo is a single, fixed-dish telescope, it has a restricted practical sensitivity to weak, quiescent emission from radio sources...
Invader From Another Galaxy
This alien intruder from another galaxy is in many ways different from other exoplanets observed by astronomers.
Located about 2000 light-years from Earth in the southern constellation of Fornax (the Furnace), the Jupiter-like planet orbits a dying star of
extragalactic origin and risks to be engulfed by it.
Power To See Most Distant Objects In The Universe
The 3C294, is one of the most distant galaxies recorded by Chandra, the most sophisticated X-ray observatory ever built.
The cluster 3C294 is even 40 percent farther (!) than the next most distant x-ray galaxy cluster.
Chandra focus on X-rays from high-energy regions of the Universe and see the invisible.
It is so sensitive that it can capture images of particles as they disappear into a black hole deep in outer space.
"Pillars Of Creation" Are Gone
Every time you look at the beautiful and famous image of the Pillars of Creation taken by Hubble back in 1995,
you are actually admiring something that no longer exists.
In fact, the Pillars of Creation were already long gone by the time the image was captured!
New Unified Theory Alters Einstein's View Of Spacetime
The scientists suggest the law of energy and momentum conservation in spacetime is valid only when normal matter, dark matter and
dark energy are all taken into account.
For normal matter alone - they say - energy and momentum are no longer conserved...
Does Triton Have a Subsurface Ocean?
Triton was discovered in 1846 by the British astronomer William Lassell, but much about Neptune’s largest moon still remains a mystery.
A Voyager 2 flyby in 1989 offered a quick peak at the satellite, and revealed a surface composition comprised mainly of water ice.