Saturn's moon Iapetus lit by Saturnshine. This is an enhanced picture; the Saturnlit is too faint to be visible to the unaided human eye.

Moon lit by Earthshine captured by the 1994 lunar prospecting Clementine spacecraft. Clementine's camera reveals (from right to left) the Moon lit by Earthshine, the Sun's glare rising over the Moon's dark limb, and the planets Saturn, Mars and Mercury (the three dots at lower left).

The phenomenon known as planetshine occurs when reflected sunlight from a planet illuminates the dark side of one of its moons. Typically, this results in the moon's dark side being bathed in a soft, faint light. The best known example of planetshine is Earthshine, which can be seen from Earth when the Moon is a thin crescent. Planetshine has been observed elsewhere in the solar system, however; in particular it has recently been used by the Cassini space probe to image portions of the moons of Saturn even when they are not lit by the Sun. Iapetus, a moon of Saturn, with its dark side illuminated by reflected light from Saturn Original caption released with image: New details on Iapetus are illuminated by reflected light from Saturn in this revealing Cassini image. ... Iapetus, a moon of Saturn, with its dark side illuminated by reflected light from Saturn Original caption released with image: New details on Iapetus are illuminated by reflected light from Saturn in this revealing Cassini image. ... Adjectives: Saturnian Atmosphere [2] Composition: ~96% molecular hydrogen ~3% Helium ~0. ... Iapetus (eye-ap-ə-təs, IPA , Greek Ιαπετός) is the third-largest moon of Saturn, discovered by Giovanni Domenico Cassini in 1671. ... Image File history File linksMetadata Ecliptic. ... Image File history File linksMetadata Ecliptic. ... Apparent magnitude: up to -12. ... Year 1994 (MCMXCIV) was a common year starting on Saturday (link will display full 1994 Gregorian calendar). ... Clementine was a joint space project between the Ballistic Missile Defense Organization (BMDO, previously the Strategic Defense Initiative Organization, or SDIO) and NASA. The objective of the mission was to test sensors and spacecraft components under extended exposure to the space environment and to make scientific observations of the Moon... The Space Shuttle Discovery as seen from the International Space Station. ... Apparent magnitude: up to -12. ... Leonardo da Vincis sketch of crescent Moon with earthshine as part of his Codex Leicester, written between 1506 and 1510. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ... Look up Limb in Wiktionary, the free dictionary. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... This article is about the planet. ... Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... The eight planets and three dwarf planets of the Solar System. ... A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... This is an artists concept of Cassini during the Saturn Orbit Insertion (SOI) maneuver, just after the main engine has begun firing. ...

Earthshine

Diagram of Earthshine

Earthshine is reflected Earthlight visible on the Moon's night side. It is also known as the Moon's ashen glow or as the old Moon in the new Moon's arms. Image File history File links No higher resolution available. ... Apparent magnitude: up to -12. ...

Leonardo da Vinci's sketch of crescent Moon with earthshine as part of his Codex Leicester, written between 1506 and 1510.

Drew Evans brilliant photo of Earthshine in April 2007.

Earthshine is most readily observable shortly before and after a New Moon, during the waxing or waning crescent phase. When the Moon is new as viewed from Earth, the Earth is nearly fully lit up as viewed from the Moon. Sunlight is reflected from the Earth to the night side of the Moon. The night side appears to glow faintly and the entire orb of the Moon is dimly visible. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The Mona Lisa Leonardo di ser Piero da Vinci (April 15, 1452 – May 2, 1519) was an Italian polymath: scientist, mathematician, engineer, inventor, anatomist, painter, sculptor, architect, musician, and writer. ... The Codex Leicester is a collection of largely scientific writings by Leonardo da Vinci. ... 1506 was a common year starting on Monday (see link for calendar) of the Gregorian calendar. ... Year 1510 (MDX) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. ... Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... The lunar phase depends on the Moons position in orbit around Earth. ... This article is about Earth as a planet. ... Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ...

Earthshine reflecting off the Moon. The bright region is directly illuminated by the sun, while the rest of the Moon is illuminated by light reflected off the Earth.

Leonardo da Vinci explained the phenomenon in the early 1500s when he realized that both Earth and the Moon reflect sunlight. Light is reflected from the Earth to the Moon and back to the Earth as Earthshine. Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... The Mona Lisa Leonardo di ser Piero da Vinci (April 15, 1452 – May 2, 1519) was an Italian polymath: scientist, mathematician, engineer, inventor, anatomist, painter, sculptor, architect, musician, and writer. ... The decade of years from 1500 to 1509, inclusive. ...

Earthshine is used to help determine the current albedo of the Earth. The data is used to analyze global cloud cover - a climate factor. Oceans reflect the least amount of light, roughly 10%. Land reflects anywhere from 10-25% of the Sun's light, and clouds reflect around 50%. So, the part of the Earth where it is daytime and from which the Moon is visible determines how bright the Moon's Earthshine appears at any given time. Albedo is the ratio of reflected to incident electromagnetic radiation. ...

Conjunction of Venus and the Moon during Earthshine

Studies of Earthshine can be used to show how the Earth's cloud cover varies over time. Preliminary results show a 6.5% dip in cloud cover between 1985 and 1997 and a corresponding increase between 1997 and 2003. This has implications for climate research, especially with regards to global warming. Some clouds have a net warming effect because they trap heat, while others have a net cooling effect because they increase albedo, so the overall effect on global temperature remains unclear. [1] Image File history File linksMetadata Earthshine. ... Image File history File linksMetadata Earthshine. ... Year 1985 (MCMLXXXV) was a common year starting on Tuesday (link displays 1985 Gregorian calendar). ... Year 1997 (MCMXCVII) was a common year starting on Wednesday (link will display full 1997 Gregorian calendar). ... Year 1997 (MCMXCVII) was a common year starting on Wednesday (link will display full 1997 Gregorian calendar). ... Year 2003 (MMIII) was a common year starting on Wednesday (link displays 2003 calendar) of the Gregorian calendar. ... Global mean surface temperatures 1850 to 2006 Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is the observed increase in the average temperature of the Earths atmosphere and oceans in recent decades and the projected... Albedo is the ratio of reflected to incident electromagnetic radiation. ...

See also: André-Louis Danjon, Danjon scale. André-Louis Danjon (April 6, 1890 – April 21, 1967) was a French astronomer born in Caen, France. ... The Danjon Scale of lunar eclipse brightness is a five-point scale useful for measuring the appearance and luminosity of the Moon during a lunar eclipse. ...

Search for terrestrial planets

Scientists at NASA's Navigator Program, which specializes in the detection of terrestrial planets, have backed the launch of a Terrestrial Planet Finder (TPF) mission.[2] TPF would detect planetshine from planets orbiting stars to investigate whether they could harbor life. It would use advanced telescope technologies to look for life-marks in the light reflected from the planets, including water, oxygen and methane. The National Aeronautics and Space Administration (NASA) is an agency of the United States government, responsible for the nations public space program. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets. ...

The European Space Agency has a similar mission, named Darwin, under consideration. This will also study the earthshine of planets to detect the signatures of life.[3] Established: 1974 Administrator: Jean-Jacques Dordain Budget: €2. ... Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. ...

Unlike many traditional astronomical challenges, the most serious challenge for these missions is not gathering enough photons from the faint planet, but rather detecting a faint planet that is extremely close to a very bright star. For a terrestrial planet, the contrast ratio of planet to its host stars is approximately ~10^-6-10^-7 in the thermal infrared or ~10^-9-10^-10 in the optical/near infrared. For this reason, Darwin and Terrestrial Planet Finder-I will work in the thermal infrared. However, searching for terrestrial planets in the optical/near infrared has the advantage that the diffraction limit corresponds to a smaller angle for a given size telescope. Therefore, NASA is also pursuing an Terrestrial Planet Finder-C mission that will search for and study terrestrial planets using the optical (and near infrared) wavelengths. While Terrestrial Planet Finder-C aims to study the planetshine of extrasolar planets, Darwin and Terrestrial Planet Finder-I will search for thermal infrared light that is reradiated (rather than scattered) by the planet, and most astronomers would not consider that be planetshine. Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets. ... Diffraction is the apparent bending and spreading of waves when they meet an obstruction. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States government, responsible for the nations public space program. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets. ... Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. ... Terrestrial Planet Finder - Infrared interferometer concept The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets. ...

In preparation for these missions, astronomers have performed detailed Earthshine observations. Astronomers have paid particular attention to whether Earthshine measurement can detect the red edge, a spectral feature that is due to the plants. The detection of a similar spectral feature in light from an extrasolar planet would be particularly interesting, since it might be due to a light-harvesting organism. While the red edge is almost certainly the easiest way to directly detect life on earth via Earthshine observations, it could be extremely difficult to interpret a similar feature due to life on another planet, since the wavelength of the spectral feature is not known in advance (unlike most atomic or molecular spectral features). Red edge refers to the region of rapid change in reflectance of chlorophyll in the near infrared range. ... Red edge refers to the region of rapid change in reflectance of chlorophyll in the near infrared range. ... This article is about the tv programme Life on Earth. ...

References

• Ford, E. B., Turner, E.L. & Seager, S. (2001) ``Characterization of extrasolar terrestrial planets from diurnal photometric variability Nature, Volume 412, Issue 6850, pp. 885-887. link and preprint
• Seager, S., Turner, E. L., Schafer, J., & Ford, E. B. (2005) ``Vegetation's Red Edge: A Possible Spectroscopic Biosignature of Extraterrestrial Plants Astrobiology, Volume 5, Issue 3, pp. 372-390. (link and preprint)
• Qiu J, Goode PR, Palle E, Yurchyshyn V, Hickey J, Rodriguez PM, Chu MC, Kolbe E, Brown CT, Koonin SE (200). "Earthshine and the Earth's albedo: 1. Earthshine observations and measurements of the lunar phase function for accurate measurements of the Earth's Bond albedo". Journal of Geophysical Research-Atmospheres 108 (D22): 4709. 

See also

• Ashen Light

The Ashen light is a glow observed on Venus somewhat similar to the phenomenon of Earthshine found on the Moon, though dimmer. ...

External links

• Science@NASA: Earthshine
• NASA Astronomy Picture of the Day, 19 April 2002
• 'Earthshine' Linked to Solar Cycle, Climate Change, Space.com
• Scientists Watch Dark Side of the Moon to Monitor Earth's Climate, American Geophysical Union