Planet Earth

Planet Earth
EUMETSAT · Attribution · source
Name	Earth
Caption	The Earth as seen from Apollo 17 and Lunar Reconnaissance Orbiter observations
Mass	5.972 × 10^24 kg
Radius	6,371 km
Period	365.25 days
Satellites	Moon
Discovered	Known in prehistory

Planet Earth Earth is the third planet from the Sun and the only known astronomical object to harbor life. It hosts complex interactions among the Moon, the Sun's radiation, and the Milankovitch cycles that drive long-term climatic variation, while human institutions such as the United Nations, NASA, and the European Space Agency study and monitor its systems.

Overview

Earth is a terrestrial planet located in the Solar System within the Milky Way galaxy and orbits the Sun at an average distance of about 1 astronomical unit. Its surface is characterized by continental crustes like Eurasia, Africa, Americas, Australia, and Antarctica, and ocean basins such as the Pacific Ocean, Atlantic Ocean, and Indian Ocean. Planetary properties are constrained by studies from missions including Voyager program, Pioneer program, and probes like Mars Reconnaissance Orbiter that provide comparative planetary data. Observational facilities such as the Hubble Space Telescope, Chandra X-ray Observatory, and ground arrays like the Very Large Telescope contribute to geophysical and atmospheric characterization.

Formation and Geology

Earth formed about 4.54 billion years ago from the solar nebula during the Late Heavy Bombardment era, with accretion processes similar to those inferred for Mercury, Venus, and Mars. Core formation produced a metallic core and silicate mantle, with differentiation evidenced by seismic studies from networks like the United States Geological Survey and the Global Seismographic Network. Plate tectonics on plates such as the Pacific Plate and the Nazca Plate reshapes the lithosphere, producing orogenies like the Himalayas and subduction zones that fuel volcanism at regions like Ring of Fire and Mount St. Helens. Rock records preserved in formations such as the Acasta Gneiss and events like the Great Oxidation Event document crustal evolution, while mineral discoveries from expeditions sponsored by institutions like the Smithsonian Institution inform models of continental growth.

Atmosphere and Climate

Earth's atmosphere is composed primarily of nitrogen and oxygen and includes layers named the troposphere, stratosphere, and mesosphere, which are monitored by satellites from programs like NOAA and missions such as ERS-1. Climate is governed by radiative forcing from the Sun, greenhouse gases including carbon dioxide and methane, and feedbacks involving ice-albedo interactions at regions like Greenland and Antarctica. Climate variability manifests in phenomena such as El Niño–Southern Oscillation, Monsoon systems, and abrupt changes recorded in ice cores from Vostok Station and EPICA. Global assessments produced by the Intergovernmental Panel on Climate Change synthesize observations, modeling from centers like the Met Office Hadley Centre, and paleoclimate proxies including tree rings in Dendrochronology and sediments from the Chesapeake Bay.

Biosphere and Ecosystems

Life on Earth spans microorganisms documented by researchers at Pasteur Institute and multicellular organisms cataloged in collections at the Natural History Museum, London and the Smithsonian Institution National Museum of Natural History. Ecosystems range from tropical rainforests in the Amazon Rainforest to coral reefs like the Great Barrier Reef, temperate woodlands of the Taiga, and freshwater basins such as the Congo Basin. Biodiversity inventories from projects like the Global Biodiversity Information Facility and conservation efforts by organizations like the World Wide Fund for Nature record species interactions, trophic structures, and evolutionary histories tied to events such as the Cretaceous–Paleogene extinction event. Human-driven initiatives including the Convention on Biological Diversity address habitat loss, invasive species, and conservation of keystone species like the African elephant and the blue whale.

Orbit, Rotation, and Magnetosphere

Earth's orbit around the Sun is slightly elliptical, with aphelion and perihelion positions influencing seasonal insolation; orbital parameters are studied via ephemerides maintained by Jet Propulsion Laboratory and the International Astronomical Union. Rotation about its axis produces day-night cycles and gradual axial precession affecting climate over millennia, as described by Milankovitch cycles. The geomagnetic field arises from dynamo action in the liquid outer core and shields against charged particles from the solar wind; interactions generate auroral displays over high-latitude regions observed by facilities such as Svalbard Global Seed Vault’s vicinity observatories and satellites like Cluster (spacecraft). Geomagnetic reversals recorded in the Geologic time scale inform studies of paleomagnetism conducted at institutions like the Geological Survey of Canada.

Human Presence and Impact

Humans expanded globally via migrations traced by work at institutions like the Max Planck Institute for Evolutionary Anthropology and archaeological sites such as Göbekli Tepe and Laetoli. Industrialization accelerated land-use change, urbanization around megacities like Tokyo, New York City, and Mumbai, and emissions that alter atmospheric composition, monitored by networks including Global Atmosphere Watch. International agreements such as the Paris Agreement and governance through the United Nations Framework Convention on Climate Change aim to mitigate anthropogenic impacts. Resource extraction in regions like the North Sea and the Amazon Basin, coupled with technologies from companies and agencies like SpaceX and Blue Origin enabling lower-cost access to space, shape contemporary interventions in Earth's systems and stewardship debates involving organizations such as Greenpeace and the World Bank.

Category:Planets of the Solar System