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Swift
2013-Feb-13, 03:15 PM
From the Journal Astrobiology (http://online.liebertpub.com/doi/abs/10.1089/ast.2012.0849) (sorry, abstract only, article behind paywall)


The search for extrasolar planets has already detected rocky planets and several planetary candidates with minimum masses that are consistent with rocky planets in the habitable zone of their host stars. A low-resolution spectrum in the form of a color-color diagram of an exoplanet is likely to be one of the first post-detection quantities to be measured for the case of direct detection.

In this paper, we explore potentially detectable surface features on rocky exoplanets and their connection to, and importance as, a habitat for extremophiles, as known on Earth. Extremophiles provide us with the minimum known envelope of environmental limits for life on our planet.

The color of a planet reveals information on its properties, especially for surface features of rocky planets with clear atmospheres. We use filter photometry in the visible as a first step in the characterization of rocky exoplanets to prioritize targets for follow-up spectroscopy.

Many surface environments on Earth have characteristic albedos and occupy a different color space in the visible waveband (0.40.9 μm) that can be distinguished remotely. These detectable surface features can be linked to the extreme niches that support extremophiles on Earth and provide a link between geomicrobiology and observational astronomy. This paper explores how filter photometry can serve as a first step in characterizing Earth-like exoplanets for an aerobic as well as an anaerobic atmosphere, thereby prioritizing targets to search for atmospheric biosignatures.


There is also an article about the work on newscientist.com (http://www.newscientist.com/article/dn23155-extreme-life-might-be-visible-on-colourful-exoplanets.html).


Seen from space, Earth gives off a large amount of near-infrared light, which is reflecting off the chlorophyll in plants. We might see a similar "red edge" on distant exoplanets if they also host green vegetation.

But Siddharth Hegde and Lisa Kaltenegger of the Max Planck Institute for Astronomy in Heidelberg, Germany, think it is possible that many rocky worlds will have extreme heat, dryness or acidity, and that hardier life forms will dominate their surfaces. So what would these organisms look like from a distance?

To find out the pair looked at the light reflected by some of Earth's more extreme life forms: lichens in arid regions, bacterial mats in very hot water and red algae in acid mine drainage. They calculated that seen from afar each type of organism would create a unique colour pattern. Lichens, for instance, appear more yellow than the algae or bacteria.

ASTRO BOY
2013-Feb-13, 09:00 PM
" So what would these organisms look like from a distance?"

This prompts me to ask the question...How reliable [at this period in time] is spectroscopy when gathering data from planetary bodies, orbiting other stars at such great distances?

Swift
2013-Feb-13, 09:06 PM
" So what would these organisms look like from a distance?"

This prompts me to ask the question...How reliable [at this period in time] is spectroscopy when gathering data from planetary bodies, orbiting other stars at such great distances?
I don't know the answer to the question, but I have an educated guess. Doing such measurements is within the realm of current technical abilities (certainly within the realm of physics), but we don't have an instrument in space that could do such measurements. I suspect that we are about two generations out from having an instrument capable of this in-space (generations of instruments, not generations of humans).

starcanuck64
2013-Feb-19, 01:28 AM
Very cool, it doesn't seem like long ago that we still hadn't detected planets in other systems and now we're looking at getting a rough idea of whether or not certain forms of life might be present on some of them.

Sorry to bring up the Sci-fi word, but this is like something out of a lot of novels I've read.

Githyanki
2013-Feb-19, 11:37 AM
I'm a fan of spectroscopy; the information's there; we just have to find it!