Earth Science Picture of the Day

Milky Way Viewed from Reunion Island

2012-01-27T03:01:00-05:00

Photographer: Luc Perrot; Luc's Web site
Summary Author: Luc Perrot; Jim Foster

This photo above shows the Milky Way as observed from Reunion Island in the Indian Ocean on the night of November 3, 2011. In the lower part of the picture, between two old tamarind trees, my silhouette is illuminated by a headlamp I'm wearing as I gaze toward the constellation of Scorpio and the galactic center. The stars that comprise Scorpio are wrapped around one of the the densest parts of our galaxy. Note that the brightest star in Scorpio, the red supergiant, Antares, is at upper left -- the tail of the scorpion curls about the tamarind at right. This is how the night sky appears in a truly dark location -- becoming increasingly more difficult to find.

Mount Baker in Filtered Sunlight

2012-01-26T03:01:00-05:00

Photographer: Robert Farrimond
Summary Authors: Robert Farrimond

Mount Baker, at 10,778 ft (3,285 m), is one of several large stratovolcanoes in Washington State. Part of the Pacific Ring of Fire, it's widely accepted that the volcanoes in this region are a result of subduction of the Juan De Fuca tectonic plate under the North American Plate. Stratovolcanoes are known for extremely violent eruptions, sometimes with far reaching effects. Mt. Baker’s last known notable eruption occurred more than 150 years ago. A field of corn ready for harvest is in the foreground. Photo taken October 8, 2011.

Photo details: Canon 1000D/XS; Shooting Mode: A-DEP; Tv (Shutter Speed): 1/4000; Av (Aperture Value): 9.5; Metering Mode: Evaluative Metering; Exposure Compensation: -2; ISO Speed: 800; Lens: EF28-105mm f/3.5-4.5 USM; Focal Length: 105.0mm; Image Quality: RAW.

Travertine

2012-01-25T03:01:00-05:00

Photographer: Wendy Van Norden
Summary Author: Wendy Van Norden

The photo above shows travertine covering the outside surface of the J. Paul Getty Museum in Los Angeles, California. In this close-up, you can clearly see leaf fossils, evidence of the shallow water environment in which the travertine formed. Rainwater becomes acidic when it absorbs carbon dioxide (CO2) from the air. As this rainwater seeps into the ground, it dissolves the calcite in limestone layers. If this water should make its way back to the surface, bubbling up from a spring, for example, the saturated groundwater would release the CO2 and precipitate the calcite around algal mats, bacteria and even leaves.

The travertine of the Getty Museum comes from the most famous travertine quarry in the world, the Bagni di Tivoli, which is located east of Rome, Italy. It's the same travertine used to build the Coliseum, the Trevi Fountain and the colonnade of Saint Peter's Basilica. This rock started forming approximately 80,000 years ago -- the quarry has been active for about the last 2,000 years. Typically, travertine is cut across the bedding planes, revealing the layering of the rock. Travertine is lighter than granite, easier to cut, and capable of carrying heavy loads. Richard Meier, the architect for the Getty Museum, didn’t need the rock to bear great weights. He chose instead to highlight the wonderful texture of the rock, so he had the rock cut parallel to the bedding planes. As a result, when visiting the Getty Museum, one is able to admire the intricate texture and abundant fossils preserved in an ancient Roman spring. Photo taken on November 13, 2011.

Photo details: Camera Maker: Apple; Camera Model: iPhone 4S; Focal Length: 4.3mm (35mm equivalent: 35mm); Aperture: f/2.4; Exposure Time: 0.0018 s (1/557); ISO equiv: 64; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Flash Fired: No (enforced); Orientation: Rotate 90; Color Space: sRGB; Software: 5.0.1.

Breccia in Death Valley

2012-01-24T03:01:00-05:00

Photographer: Rick Scott; Rick's Web site
Summary Author: Rick Scott; Jim Foster

The photo above showing a huge outcrop of breccia was taken in Fall Canyon at Death Valley National Park, California. Breccia typically forms when angular fragments (over 2mm in diameter) of rock accumulate in streambeds and alluvial fans, for instance. The pieces become bound by mineral cement or are fixed by much smaller particles that fill the spaces between the angular pieces. A debris flow is one condition where binding of the fragments can happen. Another such condition is a meteor impact crater. Breccia is similar to conglomerate, but in conglomerate the fragments are more rounded, indicating that they've traveled further (are more eroded) before cementation occurs. Photo taken on November 26, 2011.

Photo details: Camera Maker: Canon; Camera Model: Canon EOS 40D; Lens: EF16-35mm f/2.8L USM; Focal Length: 35mm; Focus Distance: Infinite; Aperture: f/8.0; Exposure Time: 0.033 s (1/30); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure Mode: Manual; White Balance: Manual; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB ; RAW Mode; Software: Adobe Photoshop CS5 Windows.

Sirius Twinkling

2012-01-23T03:01:00-05:00

Photographer: David Lynch
Summary Author: David Lynch

Twinkling is the rapid fluctuation in brightness and color of a star. It’s caused by slight changes in density of air pockets called “seeing cells” that move across the observer’s line of sight. Air’s refractive index is determined, in part, by its density. Such undulations cause slight, momentary defocusing of the starlight resulting in brightness changes, also called scintillation. In extreme cases, the star’s position hops around. Twinkling also produces rapid color changes because air is slightly dispersive, i.e. the index of refraction varies slightly with wavelength.

Both brightness and color twinkling are shown here in a five-second exposure of Sirius using a telephoto lens that was wiggled slightly during the exposure. As the star‘s twinkling image skated around the focal plane, it traced out graceful, colorful arcs, fading in some places, brightening in others.

Here scintillation and telescope jitter, the bane of astronomers everywhere, have been recast into a stunningly beautiful image. Image taken on January 4, 2012.

Rocks to Roots

2012-01-22T03:01:00-05:00

Photographer: Dale Hugo
Summary Author: Dale Hugo; Jim Foster

As shown above, in Tettegouche State Park on the North Shore of Lake Superior, Minnesota, a family of northern white cedars (Thuja occidentalis) is ganging up on a hapless granite boulder. These hardy trees need an extensive root system to handle the heavy snow loads and occasional strong winds that rake the northwestern Lake Superior area. In addition, they're often trampled by tourists during the summer months. Eventually, they and their progency will break down the boulders and rocky material, reducing it to consolidated soil more inviting to other types of trees. Weathering by root fungi plays a principal role in this slow but sure process. Frost weathering is also important in regions where freeze-thaw cycles are commonplace.

Photo details: Camera Maker: Samsung Techwin; Camera Model: <Samsung D70 / D75 / S730 / S750>; Focal Length: 17.4mm (35mm equivalent: 106mm); Aperture: f/4.9; Exposure Time: 0.0020 s (1/500); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB.

Sundog and Bright Tail Over Trento, Italy

2012-01-21T03:01:00-05:00

Photographer: Alessandro Zotta; Alessandro's Web page
Summary Author: Alessandro Zotta; Jim Foster

The photo above showing a colorful sundog heeling the horizon was taken in Trento, Italy on the afternoon of November 29, 2011. Sundogs, also known as parhelia or mock Suns, form when plate-shaped, hexagonal ice crystals in cirrus clouds are aligned horizontally. When such an alignment occurs, sunlight passes through the alternate side faces of the crystals, being bent 22 degrees from its original path. The bright tail of this sundog is actually a portion of the parhelic circle. Note that the Sun is behind the mountain face at right -- at the same altitude as the sundog.

Photo details: Nikon Camera, Model D3100; 32 mm focal length ; aperture of f/10.0; exposure time of 0.003125 s (1/320); ISO equiv: 400; exposure bias, none. Time of photo 3:44 p.m.

Was This on My Lens!?

2012-01-20T03:01:00-05:00

Photographer: Jens Hackmann
Summary Author: Jens Hackmann; Jim Foster

Have you ever looked at a picture you've taken and wondered "How in the world did THAT thing get on my lens?" In this case, the "thing" isn't a turbo-charged worm of some kind but rather an eye-catching jet condensation trail (contrail). While capturing images of the sunrise over southern Germany about 8:10 January 3, 2012, I couldn't help but notice this odd appearing contrail flying towards the Sun – off the lower left-side of the photo. Contrails take shape when hot, moist air from jet exhaust mixes with the cold ambient air, having a lower vapor pressure than the exhaust gases. As the exhaust gases cool, they condense into an artificial cloud composed of minute water droplets or ice crystals.

This contrail and the cirrus deck above the eastern horizon are sufficiently high, over 30,000 ft (9,150 m), to reflect the dawn’s early light. Wind shear to the rear of the jet is responsible for the kink in the contrail. Further behind the jet (top and top center of photo), atmospheric turbulence gives the trail its loopy look.

Photo details: Camera Maker: Canon; Camera Model: Canon EOS 5D Mark II; Lens: EF100-400mm f/4.5-5.6L IS USM; Focal Length: 400.0mm; Focus Distance: 4294967295.00m; Aperture: f/9.0; Exposure Time: 0.0063 s (1/160); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure: Manual; Exposure Mode: Manual; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: Adobe Photoshop Camera Raw 6.6 (Windows).

Lake of the Seven Cities

2012-01-19T03:01:00-05:00

Photographer: Miguel Claro; Miguel's Web site
Summary Author: Miguel Claro; Jim Foster

The three-photo panorama above features a dormant volcanic crater and the Lake of the Seven Cities on San Miguel Island in the Azore Archipelago. San Miguel is called the "Green Island" because it's the most verdant and also most populous of the Azores. Though the volcano that formed San Miguel has been extinct for approximately 400 years, its lake-filled caldera is a one of the main sources of fresh water in the archipelago and has thus facilitated the development of a number of population centers. On this nighttime long exposure, stray light from the towns surrounding the lake (actually two lakes) and reflecting off the cloud deck gives this scene a yellowish pall.

Photo details: Canon 50D camera; ISO 800; F/4; 10mm. Panorama composed of three images taken
at 2:40 a.m. on December 4, 2011; three minute exposure for each photo. Software: Adobe Photoshop CS3 Windows.

Mars Observed from a 10-inch Telescope

2012-01-18T03:01:00-05:00

Photographer: John Chumack; John’s Web site
Summary Author: John Chumack; Jim Foster

Mars is now much brighter and closer than it was just a month ago. When this image was acquired on January 5, 2012, Mars was 9.36 arc seconds in diameter, nearly twice the size it appeared in early December. From my backyard observatory near Dayton, Ohio, I could easily detect some of the Red Planet’s surface features including its north polar cap – it looked like a Christmas tree ornament hanging in the night sky. Mars is getting closer to us, and sometime between the end of February to the beginning of March it’ll be at its largest (13.8 arc seconds) during this current two-year cycle. Please don’t think Mars will ever get as big as the Moon appears, as it’s made to look in those silly images that circulate every year or so. At its closest approach, it won't look much bigger than it does now. To observe Mars, look for it well after nightfall in the eastern sky, near the constellation of Leo. The shot above was captured with a 10 in (25 cm) telescope on the morning of January 5, 2012 at approximately 7:00.

Photo details: 10-inch Meade SCT telescope; DMK 21AF04 fire-wire Camera (640x480); 2x Barlow lens; 3,300 frames stacked in Registax6.