atmosphere – A Darker View

The Most Reviled of Scientific Instruments

Scientific instruments have a habit of presenting us with uncomfortable truths. Galileo’s telescopes showed that our solar system did not conform to the prevailing teachings of the day. The great particle accelerators show a complexity underlying reality that defies a simple explanation of the universe. Likewise an almost forgotten instrument sitting atop a volcano has shown that humans have altered our world in very damaging ways.

NOAA Mauna Loa Climate Observatory — The NOAA Mauna Loa Climate Lab in the light of dawn

I had driven to the top of Mauna Loa for a session of Geminid meteor watching and photography, joining Steve, a local photographer and friend for a cold, beautiful morning atop the mountain. As we were about to leave another friend drove past. Ben used to work with me at Keck and now tends the solar observatory adjacent to the NOAA climate laboratory. Looking at the sky and the drizzling fog that had rolled in with the dawn he noted that it would be a while before he could open the telescope. Instead he offered us a tour.

It was in the main building that we stopped to look at a little instrument parked rather oddly in the hall. Not much, a simple box with a few aluminum tubes and a bit of circuitry and wiring. It took me a moment to realize I was looking at a piece of scientific history. Here was the Scripps Carbon Dioxide Analyzer that has provided the data that has changed our relationship with our planet.

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Water Vapor Detected in the Atmosphere of a Hot Jupiter

W. M. Keck Observatory press release…

California Institute of Technology (Caltech) astronomers using data gathered at the W. M. Keck Observatory have developed a new technique for planetary scientists that could provide insight into how many water planets like Earth exist within our universe. The results have been published on February 24th by The Astrophysical Journal Letters.

Exoplanet Water Spectra — Simulated data showing the method used for detecting water vapor features detected around the hot Jupiter tau Boo b.
Credit: Alexandra Lockwood (CalTech) background image used with permission from David Aguilar (CFA)

Scientists have detected water vapor on other planets in the past, but these detections could only take place under very specific circumstances, according to graduate student Alexandra Lockwood, the first author of the study. “When a planet transits, or passes in orbit, in front of its host star, we can use information from this event to detect water vapor and other atmospheric compounds. Alternatively, if the planet is sufficiently far away from its host star, we can also learn about a planet’s atmosphere by imaging it.”

However, a significant portion of the population of extrasolar planets does not fit either of these criteria and there wasn’t really a way to find information about the atmospheres of these planets. Looking to resolve this problem, Lockwood and her advisor Geoffrey Blake—Caltech professor of cosmochemistry, planetary sciences and chemistry—were inspired by the recent detection of carbon monoxide in the extrasolar planet, tau Boo b and they wondered if they could detect water in a similar manner.

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Sifting Through the Atmospheres of Far-off Worlds

JPL press release…

HR8799 — Three exoplanets orbiting a young star 140 light years away are captured using Keck Observatory’s near-infrared adaptive optics. Image credit Christian Marois, NRC and Bruce Macintosh, LLNL

Gone are the days of being able to count the number of known planets on your fingers. Today, there are more than 800 confirmed exoplanets — planets that orbit stars beyond our sun — and more than 2,700 other candidates. What are these exotic planets made of? Unfortunately, you cannot stack them in a jar like marbles and take a closer look. Instead, researchers are coming up with advanced techniques for probing the planets’ makeup.

One breakthrough to come in recent years is direct imaging of exoplanets. Ground-based telescopes have begun taking infrared pictures of the planets posing near their stars in family portraits. But to astronomers, a picture is worth even more than a thousand words if its light can be broken apart into a rainbow of different wavelengths.

Those wishes are coming true as researchers are beginning to install infrared cameras on ground-based telescopes equipped with spectrographs. Spectrographs are instruments that spread an object’s light apart, revealing signatures of molecules. Project 1640, partly funded by NASA’s Jet Propulsion Laboratory, Pasadena, Calif., recently accomplished this goal using the Palomar Observatory near San Diego.

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Pits in the Ice

You know it is cold when the very air starts to freeze.

This is what happens in a Martian winter when no sunlight reaches the polar region. It grows so cold that the atmosphere, mostly carbon dioxide, begins to freeze and fall to the ground as snow. Frozen carbon dioxide, dry ice, accumulates into a permanent polar cap. While the extent of this polar cap waxes and wanes with the Martian seasons, there is always some ice.

The image below, taken by the HiRISE camera aboard the Mars Reconnaissance Orbiter shows of a section of the southern permanent polar cap. Late summer has caused much of the polar cap to sublimate (convert back to gas), exposing some of the rock under the ice.

Here much of the terrain is shaped by the annual freeze and thaw cycles. These pits are probably the result of these cycles and are about 60m (200ft) across. Soon the region will return to the darkness of winter and the pits will be re-buried in the ice.

Pits in the Polar Cap — Pits in the southern Martian polar cap exposed by late summer sunlight, image taken July 29th 2011, credit: NASA/JPL/University of Arizona

Mercury in the Sunset

Earlier this month, as Mercury was slipping back into the glare of the Sun, I had an opportunity to shoot some webcam material of the planet in hopes of getting an image of the crescent shape. The resulting image does not look like much, but I have to think it really isn’t all that bad.

The photo does represent Mercury fairly well, at least the normal view you get in a telescope. As the innermost planet does not get very far from the Sun, it is typically seen quite low on the horizon. This leads to poor views seen through a great deal of atmospheric distortion.

What the photo does not show is the chromatic distortion, this was corrected during processing of the photo. The atmosphere will also break up the color, refracting the light when an object is low on the horizon. The processing software allows realigning the color planes, correcting much of the effect.