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Bouguer gravity anomaly map over the Chicxulub impact crater. The coastline is designated by a thin white line, cenotes (natural pits) and sinkholes are designated by black dots, and the city of Mérida and the town of Chicxulub Puerto are designated…

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from article Chicxulub impact crater

Seismic line imaging of what lies beneath the seafloor, showing the Chicxulub impact crater. The crater includes many faults that can be grouped into an exterior ring fault, a series of outer ring faults, and a series of inner ring faults. Within…

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from article Graptolithina

Sketches of portions of pterobranch and graptolite colonies showing the dwelling tubes and the constructional units of the graptolite skeleton. (a) Young Rhabdopleura compacta colony with founder zooid and first asexual bud (Recent). Benthic…

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from article Graptolithina

Scanning electron micrograph of a graptolite (Pseudoclimacograptus scharengergi) showing the fuselli (horizontal ridges) that compose graptolite thecae, and the cortical bandages (oblique strips) that were deposited on top of the fuselli (Middle…

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from article Graptolithina

Hypothetical form of zooids that inhabited colony tubes, based on a planktic graptolite. Large zooids are shown with possible oarlike swimming organs used to move the colony through the ocean water and tentacles for feeding. Also shown are two…

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from article Graptolithina

Examples of some planktic graptolites, reconstructed to show three-dimensional form.

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from article Ursa Minor

Modern boundaries of the constellation Ursa Minor, the Little Bear. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension…

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from article Venus

Venus compared to Earth in size. Note that the image of Venus at left does not include the planet's thick, opaque atmosphere. The image was obtained by the Magellan spacecraft that orbited Venus from 1990 to 1994. Magellan used cloud-penetrating…

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from article Venus

Venus viewed in visible light by the Galileo spacecraft during a 1990 gravity assist flyby on the probe's ultimate journey to Jupiter. (Credit: NASA)

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from article Venus

Global Venus clouds, as viewed in the ultraviolet from Venus Express. These features can be used to track winds and atmospheric motion at the cloud tops. Convection clouds can be seen near the equator (top of image), whereas streaky brighter clouds…

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from article Venus

Inhomogeneities in the total thickness of the clouds between 48 and 70 km (30 and 43 mi) show up in the near-infrared. These clouds, seen only at night, are backlit from the hot atmosphere below it (similar to a Chinese lantern), where bright…

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from article Venus

Perspective view of the southern boundary of Laksmi Planum, a plateau 2.5–4.0 km (1.5–2.5 mi) high. (Credit: NASA/JPL)

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from article Venus

Magellan image of the central and northern parts of the highland region Ovda Regio (north at top). Ridges running approximately east-west (horizontally) have been interpreted as resulting from crustal shortening (compression). Ridges are cut by…

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from article Venus

Perspective view of a portion of the Western Eistla Regio, with a rift valley in the foreground and the volcanoes Gula Mons (right) and Sif Mons (left) on the horizon. (Credit: NASA/JPL)

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from article Venus

Sapas Mons, one of several large volcanic edifices that compose the broad equatorial rise known as Alta Regio. (Credit: NASA/JPL)

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from article Venus

Computer-simulated perspective view, based on data from Magellan spacecraft, showing three impact craters in the northwestern portion of Lavinia Planitia with diameters ranging from 37 to 63 km (23 to 39 mi). (Credit: NASA/JPL)

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from article Palaeonisciformes

Mimia toombsi (Gardiner & Bartram, 1977), Late Devonian, Gogo, Australia. One of the earliest palaeonisciforms, reaching 15 cm (6 in.) long, and known by complete fossils. (Reprinted with permission from B. G. Gardiner, The relationships of the…

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from article Palaeonisciformes

Chirodus granulosus (Young, 1866) was a deep-bodied palaeonisciform that grew to 10 cm (4 in.) and lived in Carboniferous coal swamps of Britain. The teeth formed cutting blades that may have been used to crop vegetation. This reconstruction is…

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from article Astronomy

A photograph of the Milky Way in the night sky over the ESO 3.6-metre telescope, at right, at the La Silla Observatory in northern Chile. [Credit: ESO/B. Tafreshi ( twanight.org )]

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from article Astronomy

An artist’s impression of the exoplanet GJ 504, a world several times the size of Jupiter and anticipated to have a magenta color, still glowing from its initial formation. (Credit: NASA's Goddard Space Flight Center/S. Wiessinger)

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from article Astronomy

The Hubble Space Telescope in orbit above Earth. (Credit: NASA)

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from article Orbital motion

Orbital motion in a plane, in the shape of an ellipse, with the primary body at the focus F.

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from article Orbital motion

Orbit oriented in space with respect to a fundamental plane, in this case the celestial equator.

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from article Cladoselache

Cladoselache fyleri, from the Upper Devonian of Cleveland. (After S. E. Bendix-Algreen, 1975)

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from article Paleocopa

Paleocopa. (a) Ogmoopsis nodulifera, left valve; from the Ordovician of Sweden. (b) Eurychilina subradiata, right valve showing wide complete frill; Ordovician of Minnesota. (c) Sulcicuneus porrectinatium, male and female carapaces; Devonian of…

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