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Researchers have reached a key new milestone in the continuing search for worlds like Earth that could support life elsewhere in the universe. For the first time, water vapor has been detected in the atmosphere of an exoplanet that resides within…

One of the large self-gravitating aggregates of stars, gas, dust, planets, rocks, and dark matter that occurs by the hundreds of billions in the universe, collectively containing most of the cosmos' visible matter. Everywhere we look beyond our own…

How the diverse array of galaxies that are now observed originated and evolved into their present form. Deep telescope observations of the cosmos have found evidence for the first galaxies arising within several hundred million years after the big…

The study of gamma rays of cosmic origin. Gamma rays are the highest energy form of light. They comprise a vast spectral domain extending from an energy of 0.01 MeV (megaelectronvolts, corresponding to a wavelength of 10−10 m, the adopted boundary…

The discipline of Earth science that investigates the chemical composition of the Earth, other planets, and the universe as a whole, as well as the chemical processes that occur within them. Geochemistry is important because basic knowledge about…

Computer-based technologies for storing, manipulating, and analyzing geographically referenced information. Attribute information and spatial information are integrated in geographic information systems (GIS) through the notion of a data layer,…

The science of the Earth. The study of the Earth's materials and of the processes that shape them is known as physical geology. Historical geology is the record of past events. Earth Earth sciencesEnergy from two sources continually produces changes…

The study of landforms, including the description, classification, origin, development, and history of planetary surface features. Emphasis is placed on the interpretation of the erosional and depositional features of the Earth's surface. However,…

Thermal or electrical power produced from the thermal energy contained in the Earth (geothermal energy). Use of geothermal energy is based thermodynamically on the temperature difference between a mass of subsurface rock and water and a mass of…

Researchers surveying ice loss from 650 glaciers across a 2000-kilometer (1240-mile) west-to-east expanse of the Himalayan Mountains reported in the journal Science Advances (June 2019) significant melting caused by global climate change over the…

A broad field encompassing all aspects of the study of ice. Many glaciologists focus their attention on glaciers, the largest ice masses on Earth, but glaciology also includes the study of ice that forms on rivers, lakes, and the sea; ice in the…

Significant and persistent changes in the state of Earth’s climate. Earth's past climates, or paleoclimates, have alternated between ice ages and periods warmer than today over relatively long time scales (millions to tens of millions of years)…

The rise in the surface temperature of the Earth. Global warming is one of the names given to the systematic increase of globally averaged surface temperature that has been measured since the mid-nineteenth century. There is abundant evidence that…

Attempts to unify three fundamental interactions—strong, electromagnetic, and weak—into one interaction at some very high energy. Also referred to as Grand Unified Theory, grand unification theories (GUTs) posit that three out of the four recognized…

The late stage in stellar evolution in which the pressure in a star is insufficient to maintain the star at a stable size. During gravitational collapse, material in an aged star falls inward under its own gravitational attraction. Depending on the…

All freshwater comes from precipitation over land, which is distributed on Earth as blue and green water. Blue water—that is, surface and groundwater—is stored as freshwater in lakes, streams, ice, and snow, as well as below ground. Green water is…

The most famous of comets, associated with many important events in history. A comet is a small body, consisting of rock and ice, whose orbit takes it near enough to the Sun that its ice begins to sublimate, oftentimes generating a bright atmosphere…

A large, space-borne astronomical observatory that studied the “cold” universe in the far infrared and submillimeter portions of the electromagnetic spectrum. The Herschel Space Observatory was a major mission in the European Space Agency (ESA)…

The study of the universe as revealed by the high-energy, invisible forms of light, x-rays and gamma rays, and through cosmic rays and neutrinos. High-energy forms of radiation and particle emissions are produced through the heating and acceleration…

The largest visible-light observatory ever placed into space. The Hubble Space Telescope's orbit, some 612 km (380 mi) above Earth's surface (Fig. 1), keeps it beyond almost all of Earth's atmosphere, at a location where its view of the heavens is…

A mineral with the chemical composition MnWO4. Hübnerite (sometimes spelled huebnerite) is the manganese member of the wolframite solid-solution series. It commonly contains small amounts of iron. It occurs in monoclinic, short, prismatic crystals.…

A tropical cyclone with maximum sustained winds that reach or exceed a threshold of 119 km/h (74 mi/h). In the western North Pacific Ocean such a storm is known as a typhoon and in other parts as a severe tropical cyclone. Many tropical cyclones do…

Accelerating fluxes and stores of water in the atmosphere, oceans, and land regions because of global warming. Figure 1 shows the primary hydrologic cycle compartments and fluxes. The total volume of water in the Earth system is approximately 1.36 ×…

A large mass of glacial ice broken off and drifted from parent glaciers or ice shelves along polar seas. Icebergs are distinguished from polar pack ice, which is sea ice, and from frozen seawater, whose rafted or hummocked fragments may resemble…

A theory motivated by considerations from elementary particle physics and problems in standard big bang cosmology, which asserts that the early universe underwent a rapid period of exponential expansion. Inflationary theories predict that the scale…

The field of astronomical observations specializing in detecting photons from the infrared portion of the electromagnetic spectrum. Infrared astronomy plays an important role particularly in the study of cooler astrophysical objects, ranging from…

Researchers Chi Ma of Caltech and Alan Rubin of the University of California at Los Angeles reported in the journal American Mineralogist (September 2019) the discovery in a meteorite of the first natural occurrence of the iron-carbide mineral…

Earth’s surface temperature is warming, and the Arctic region is warming even faster. Yet winters in the mid-latitudes of Asia, Europe, and the United States have been colder than average, thanks to blasts of record-breaking frigid air caused by…

After reports that June 2019 was the warmest June on record, July 2019 followed with the dubious distinction that it was the warmest month since atmospheric temperature record-keeping began in 1880, according to the U.S. National Oceanic and…

A space telescope mission dedicated to detecting exoplanets. The tenth mission launched under the National Aeronautics and Space Administration's (NASA's) Discovery Program, Kepler was the agency’s first mission dedicated to the search for planets…

A reservoir of icy bodies just beyond the orbit of the planet Neptune. The Kuiper Belt (Fig. 1) is the largest observed relatively stable ensemble of small bodies in the planetary region, outnumbering the rocky main-belt asteroids between Mars and…