Satellite Eye on Earth: May 2017 – in pictures

vertical view of Vesuvius in southern Italy, taken by the European Space Agency (ESA) astronaut Thomas Pesquet from the International Space Station. The Proxima mission is named after the closest star to the sun, continuing a tradition of naming missions with French astronauts after stars and constellations. The mission is part of the ESA’s plan to use Earth-orbiting spacecraft as a place to live and work while preparing for future voyages of exploration further into the solar system.

Garabogazköl
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Photograph: OLI/Landsat 8/Nasa

The next time you are out at sea, keep an eye out for long filaments of foam and debris floating on the surface. This common phenomenon – usually the product of natural decomposition processes and wind – is seen on Garabogazköl, a shallow, salty lagoon near the Caspian Sea in Turkmenistan. In most cases, foam is the product of decaying aquatic plants, algae, phytoplankton, or other microorganisms. The decomposition process releases oils and other substances called surfactants that rise up and reduce the surface tension of the water, making it easier for bubbles to form in windy conditions. (In addition to these natural sources, detergents and other manmade pollutants can act as surfactants.) In the case of Garabogazköl, the white lines are likely the intersections of warmer and cooler waters. When two surface currents bump into each other, they dive.

Monterrey, Mexico
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Photograph: ISS/Nasa/ESA

Mount Silla – also referred to as Cerro de la Silla or Saddle Hill– is an iconic landscape feature of the Monterrey, the capital of the Mexican state of Nuevo León. When viewed from the west, the ridges and peaks resemble a saddle. Mount Silla has been declared a natural monument under the guidelines of the World Commission on Protected Areas. The Monterrey metropolitan area sits 1,300 meters (4,200 feet) below the steep, forested flanks of the mountain. Monterrey straddles several large rivers flowing out of the mountains. The Santa Catarina river cuts through the older parts of the city (such as Monterrey Antiguo). Major highways follow the river to the nearby cities of Guadalupe, San Pedro Garza, and Santa Catarina. Rio La Silla (Saddle river) flows from the northern Sierra Madre Oriental mountain range and joins the Santa Catarina just outside the top left corner of the image. The semi-arid climate keeps these rivers dry for much of the year. Nuevo León state is home to the third largest economy in Mexico thanks to Monterrey’s extensive manufacturing facilities and infrastructure.

Flooding along the Mississippi, Missouri, and Illinois rivers. At the time, the Mississippi was transitioning from moderate to minor flood stage. For comparison, the first image shows the three rivers a year earlier.

Lake Natron
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Photograph: OLI/Landsat 8/Nasa

Not many people venture near the shores of Lake Natron in northern Tanzania. The lake is mostly inhospitable, except for a few species adapted to its warm, salty, and alkaline water. The lake is seen here very early in the rainy season that runs from March to May. The climate here is arid. In a non-El Niño year, the lake receives less than 500mm (20in) of rain. Evaporation usually exceeds that amount, so the lake relies on other sources – such as the Ewaso Ng’iro river at the north end – to maintain a supply of water through the dry season.

But it is the region’s volcanism that leads to the lake’s unusual chemistry. Volcanoes, such as Ol Doinyo Lengai (about 20km to the south), produce molten mixtures of sodium carbonate and calcium carbonate salts. The mixture moves through the ground via a system of faults and wells up in more than 20 hot springs that ultimately empty into the lake. While the environment is too harsh for most common types of life, there are some species that take advantage of it. Small, salty pools of water can fill with blooms of haloarchaea – salt-loving microorganisms that impart the pink and red colours to the shallow water. And when the waters recede during the dry season, flamingos favour the area as a nesting site as it is mostly protected from predators by the perennial moat-like channels and pools of water.

Gobi Desert in China’s Gansu Province
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Photograph: ISS/Nasa/ESA

Drainage patterns are visible on the south-western end of the Gobi desert in China’s Gansu province. The desert landscape – part of the Hexi corridor along the historical Silk Road – is low in elevation, generally flat, and surrounded by mountains and rolling hills. The foothills of the Tien Shan mountains lie to the north. As temperatures warm in the spring, snow melt from the higher elevations flows down into streams, forming narrow alluvial fans. The water carries sand, silt, and clay that accumulate at the mouths of the streams. These sediments are then available for further transport by larger valley rivers such as the Shule. The grid pattern superimposed on the basin is part of the Gansu wind farm project. Narrow roads mark the paths between dozens of wind turbines. Currently China is the largest emitter of greenhouse gases, and the wind farms are part of an effort to reduce carbon emissions and to harness cleaner energy. Several small towns skirt the Shule river, diverting water for cultivation of wool, tobacco, and a variety of grain and fruit crops.

Phytoplankton blooms in the waters around Britain and France.
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Photograph: VIIRS/Suomi NPP/Nasa

Phytoplankton blooms in the waters around Britain and France. Increasing sunlight in the spring provides the energy for the floating, microscopic plant-like organisms to bloom in vast numbers.

These images show differences in night-time lighting between 2012 and 2016 in Syria and Iraq, among several Middle Eastern countries. Such images can indicate economic development or the lack of it. Some changes reflect increases or decreases in electric power generation or in the steadiness of the supply.

Night light images also have value for international relief and humanitarian organisations, which can use this data to pinpoint areas in need. Nasa makes its Earth observations openly available to those seeking solutions to important global issues.

In the above images, the changes are most dramatic around Aleppo, but also extend through western Syria to Damascus. Over the four years, lighting increased in areas north of the Syrian border in Turkey and to the west in Lebanon. According to a 2015 report from the Voice of America, as much as 80 percent of the lights have gone out in Syria over the past few years.

In Iraq, some northern sections near Mosul saw a decrease in light, while areas around Baghdad, Irbil, and Kirkuk saw increases. Note, too, the change in electric light patterns along the Tigris and Euphrates river basins.

South America
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Photograph: Modis/Terra/Nasa

By late autumn the temperatures in southern South America begin to turn chilly and grasses develop the first traces of the brown colouration of senescence as they start to wilt and dry. It is also the time when precipitation increases as the season heads into winter. A broad bank of open-celled marine cumulus clouds covers the South Pacific. Thick clouds also hang over the Andes, obscuring all of Chile (along the west coast) and much of western Argentina. Smaller clumps of cloud are scattered across the semi-desert of Argentina – some reaching over the Argentine Sea.

Mokpo and islands
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Photograph: Proba-V/Vito/ESA

Mokpo is a city of 250,000 inhabitants in the south-west of South Korea. It is a main gate to the country’s largest granary at the Honam plain and was a naval base during the Joseon dynasty (1392–1910). The port city is surrounded outside the coast by more than 1,400 islands, which provide fishing grounds and also protect the area from large typhoon and tsunami impacts. Mokpo lies in the bottom right of the image, a blue-grey area located at the Yeonsang river estuary. Scattered smaller and larger islands lie off the coast, while an extensive area with large sediment concentrations extends further into the Yellow Sea in a bow shape.