Thirteen years ago, a satellite acquired this beautiful image (above) of light and sand playing off a portion of the ocean floor in the Bahamas. The caption that accompanied the image didn’t include many details, only noting that the image was acquired by the Enhanced Thematic Mapper Plus (ETM+) sensor on Landsat 7 and that, “tides and ocean currents in the Bahamas sculpted the sand and seaweed beds into these multicolored, fluted patterns in much the same way that winds sculpted the vast sand dunes in the Sahara Desert.”
An image as beautiful as this seemed like it deserved a bit more explanation, so I grabbed a recent (January 9, 2014) scene of the same area captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. That image (below) shows a much broader view of the area. You can still see some details of the intricate network of dunes, but the MODIS image offers a much better sense of the regional geology. For instance, you can easily see that the section of dunes shown in the first image (the white box in the lower image) is part of a much larger limestone platform called the Great Bahama Bank. Limestone is a sedimentary rock formed by the skeletal fragments of sea creatures, including corals and foraminifera, and this particular limestone platform has been accumulating since at least the Cretaceous Period.
You can also see a sharp division between the shallow (turquoise) waters of the Great Bahama Bank and the much deeper (dark blue) parts of the ocean. The submarine canyon that separates Andros Island from Great Exuma Island is nearly cut off entirely from the ocean by the Great Bahama Bank, but not quite. A connection to deep waters to the north gives the trench the shape of a tongue, earning the feature the name “Tongue of the Ocean.” At its lowest point, the floor of the Tongue of the Ocean is about 14,060 feet (4,285 meters) lower than Great Bahama Bank. The shallowest (lightest) parts of the the feature, in contrast, are just a few feet deep.
Last week, a city-state sized chunk of ice broke off of Pine Island Glacier (PIG), sending iceberg B-31 into a bay off West Antarctica. Though the formation of the 700 square-kilometer iceberg could be a purely natural event — the result of a floating ice tongue growing too long and losing its balance on the sea — some scientists suspect that changes in Pine Island Glacier are due to changing conditions below.
Hindus are celebrating Diwali this week. That means cities and towns around the world—but particularly in South Asia—are ablaze with lamps, candles, and firecrackers. It’s also become a tradition (of sorts) to share a colorful image via social media that was supposedly taken by a satellite during Diwali. If that image turns up on your feed, be skeptical.
As we pointed out last year, that image is a composite created and colored back in 2003 by NOAA scientists to illustrate population growth over time. In reality, India during Diwali looks something more like the image you see at the bottom of this page. The fact is that any extra light produced during Diwali would be so subtle that it would be extremely difficult to detect from space.
One year ago today, citizens of New Jersey, New York, Connecticut, and much of the northeastern United States woke up to flooded avenues and homes, wind-ravaged neighborhoods, blackouts, and ripped up trees, coastlines, and lives. In the dark, early hours of October 30, 2012, the VIIRS instrument on the Suomi NPP satellite caught this glimpse of the monster storm named Sandy, a hurricane that collided with two other weather fronts and merged into one of the most destructive storms in recorded American history.
Our gallery of Sandy images conveys an abstract, distant sense of the event. In satellite images, the eye is drawn to the awesome and beautiful cloud forms; to the potent, organized march across the skies; to the incredible scale of the storm. But the shoreline of my New Jersey childhood was nearly wiped clean, and a satellite can’t really show that. It’s not until you get down to the street lev