Fall Book Review II—Elaboration upon Frontiers of Astrobiology (chapter 13)

Post based upon an elaboration of a chapter in the book: Frontiers of Astrobiology,  (Characterizing Exoplanet Atmospheres, chapter 13 author—Giovanna Tinnetti) [Drs. Impey, Lunine & Funes –editors (Cambridge University Press 2012)]. I hope to further elaborate upon a handful of other chapters, as well.

As I interpret bits-and-pieces of the text in an erudite manner (for reader consumption), I am reminded that anyone pick-up a book, read it and regurgitate the contents. (I hope to provide insight into the text and give some of the book’s flavor to you.)

The author of chapter 13 draws the reader into exo-planet spectral characterization—specifically stating the case for ESA’s future probe, EcHO.


Let’s Speak of Exo-planets and their Spectroscopy

Current space-based telescopes do not possess the technological capabilities for spectral analysis of distant “earth-like” exo-planets.

In spite of the recent breakthrough in exo-planet imaging, of the planet Kepler 7b, astrobiologists need to utilize technological breakthroughs (in parallel fields) to advance their paradigms. The cloud map of Kepler 7b could not be discerned further for it components. (below):

Kepler-7b (left), which is 1.5 times the radius of Jupiter (right), is the first exoplanet to have its clouds mapped. The cloud map was produced using data from NASA’s Kepler and Spitzer space telescopes. Image Credit: NASA/JPL-Caltech/MIT

Image URL: http://www.astrobio.net/pressrelease/5720/patchy-clouds-on-an-exotic-world

The cloud map of Kepler 7b is obtained in part from reflected light (the host star is utilized as a light source for cloud discernment).

Using the website description of the “cloud map”—

“Kepler’s visible-light observations of Kepler-7b’s Moon-like phases led to a rough map of the planet that showed a bright spot on its western hemisphere. But these data were not enough on their own to decipher whether the bright spot was coming from clouds or heat. The Spitzer Space Telescope played a crucial role in answering this question. . . . Spitzer’s ability to detect infrared light means it was able to measure Kepler-7b’s temperature, estimating it between 1,500 and 1,800 degrees Fahrenheit (1,100 and 1,300 Kelvin). This is relatively cool for a planet that orbits so close to its star — within 0.06 astronomical unit — and, according to astronomers, too cool to be the source of light Kepler observed. Instead, they determined, light from the planet’s star is bouncing off cloud tops located on the west side of the planet. “Kepler-7b reflects much more light than most giant planets we’ve found, which we attribute to clouds in the upper atmosphere,” said Thomas Barclay, Kepler scientist at NASA’s Ames Research Center in Moffett Field, Calif. “Unlike those on Earth, the cloud patterns on this planet do not seem to change much over time — it has a remarkably stable climate.”

Nominally speaking, the cloud map of Kepler 7b seems to indicate a non-habitable world. For sake of argument, how can “we” further discern cloud characteristics of Kepler 7b? What are the component(s) of the clouds? Infrared spectroscopy is key to Kepler 7b’s component characterization. The duty may eventually fall to the next generation of space-based telescopes.

Let’s speak briefly of EcHO

EcHO (when and if launched) provides an unprecedented view of the components of exo-planet atmospheres—namely, the successful quest of a habitable exo-world is paramount to de-provincializing the Earth. Our planet, in many ways, is much the way that Galileo would have interpreted it centuries ago—so much so that we “still” consider ourselves the only kids on the block. EcHO, when successfully deployed, will possess the ability to characterize stellar companions similar to ones in our Solar System. The manner of discernment is to image the planet(s) via transit spectroscopy—in short staring at a part of the sky known to possess an exo-solar system.




Cambridge University Press Link to the Book




October 2012, Volume 34, Issue 2, pp 311-353


Tinetti, G. et al

(135 authors total)


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