24 Themis
Encyclopedia
24 Themis is one of the largest main-belt asteroid
s. It is also the largest member of the Themistian asteroid family
. It was discovered by Annibale de Gasparis
on April 5, 1853. It is named after Themis
, the personification of natural law and divine order in Greek mythology
.
of Naples
, though it was given its name by fellow Italian astronomer Angelo Secchi
. The asteroid was named after Themis
, the Greek goddess of law. Gravitational perturbations in the orbit of Themis were used to calculate the mass of Jupiter
as early as 1875.
On 24 December 1975, 24 Themis had a close encounter with 2296 Kugultinov
with a minimum distance of 0.016 AU. By analyzing the perturbation of Kugultinov's orbit due to the gravitational pull of Themis, the mass of Themis was determined to be approximately 2.89 solar masses.
with an eccentricity
of 0.1306 and an inclination
of 0.76°. It has an orbital period
of 5.54 years. The distance between Themis and the Sun ranges from 2.71 AU
at perihelion and 3.55 AU at aphelion, with a mean distance of 3.1302 AU. Themis is part of the Themis family
of asteroids, which is located in the outer part of the main belt. The family consists of a core of large objects surrounded by a cloud of smaller objects; 24 Themis is a member of the core.
was confirmed on the surface of this asteroid
using NASA
’s Infrared Telescope Facility
. The surface of the asteroid appears completely covered in ice. As this ice
layer is sublimated, it may be getting replenished by a reservoir of ice under the surface. Organic compounds were also detected on the surface.
Scientists hypothesize that some of the first water brought to Earth
was delivered by asteroid impacts after the collision that produced the Moon
. The presence of ice on 24 Themis supports this theory. Because of its proximity to the sun (~3.2 AU), the widespread ice on the surface of 24 Themis is somewhat unexpected. The surface ice may be replenished by a sub-surface reservoir of water or impact gardening
—a lunar phenomenon in which the moon overturns surface material at a rate of 1 m/ Gyr.
An alternative mechanism to explain the presence of water
ice on 24 Themis is similar to the hypothesized formation of water on the surface of the Moon
by solar wind
. Trace amounts of water would be continuously produced by high-energy solar proton
s impinging oxide
minerals present at the surface of the asteroid
. The hydroxyl
surface groups (S–OH) formed by the collision of protons (H+) with oxygen
atoms present at oxide surface (S=O) can further be converted in water molecules (H2O) adsorbed onto the oxide minerals surface. The chemical rearrangement supposed at the oxide surface could be schematically written as follows:
or,
where S represents the oxide surface.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
s. It is also the largest member of the Themistian asteroid family
Themis family
The Themis or Themistian Asteroid Family is a Hirayama family of asteroids found in the outer portion of the main asteroid belt, between the orbits of Mars and Jupiter. At a mean distance of 3.13 AU from the Sun, it is one of the more populous asteroid families...
. It was discovered by Annibale de Gasparis
Annibale de Gasparis
Annibale de Gasparis was an Italian astronomer. From 1864 to 1889 he was the director of the Astronomical Observatory of Capodimonte in Naples.He won the Gold Medal of the Royal Astronomical Society in 1851....
on April 5, 1853. It is named after Themis
Themis
Themis is an ancient Greek Titaness. She is described as "of good counsel", and is the embodiment of divine order, law, and custom. Themis means "divine law" rather than human ordinance, literally "that which is put in place", from the verb τίθημι, títhēmi, "to put"...
, the personification of natural law and divine order in Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
.
Discovery and observations
24 Themis was discovered on 5 April 1853 by Annibale de GasparisAnnibale de Gasparis
Annibale de Gasparis was an Italian astronomer. From 1864 to 1889 he was the director of the Astronomical Observatory of Capodimonte in Naples.He won the Gold Medal of the Royal Astronomical Society in 1851....
of Naples
Naples
Naples is a city in Southern Italy, situated on the country's west coast by the Gulf of Naples. Lying between two notable volcanic regions, Mount Vesuvius and the Phlegraean Fields, it is the capital of the region of Campania and of the province of Naples...
, though it was given its name by fellow Italian astronomer Angelo Secchi
Angelo Secchi
-External links:...
. The asteroid was named after Themis
Themis
Themis is an ancient Greek Titaness. She is described as "of good counsel", and is the embodiment of divine order, law, and custom. Themis means "divine law" rather than human ordinance, literally "that which is put in place", from the verb τίθημι, títhēmi, "to put"...
, the Greek goddess of law. Gravitational perturbations in the orbit of Themis were used to calculate the mass of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
as early as 1875.
On 24 December 1975, 24 Themis had a close encounter with 2296 Kugultinov
2296 Kugultinov
2296 Kugultinov is a main-belt asteroid discovered on January 18, 1975 by L. Chernykh at Nauchnyj.- External links :*...
with a minimum distance of 0.016 AU. By analyzing the perturbation of Kugultinov's orbit due to the gravitational pull of Themis, the mass of Themis was determined to be approximately 2.89 solar masses.
Orbit and rotation
Themis is in an elliptical orbit around the SunSun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
with an eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
of 0.1306 and an inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
of 0.76°. It has an orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
of 5.54 years. The distance between Themis and the Sun ranges from 2.71 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
at perihelion and 3.55 AU at aphelion, with a mean distance of 3.1302 AU. Themis is part of the Themis family
Themis family
The Themis or Themistian Asteroid Family is a Hirayama family of asteroids found in the outer portion of the main asteroid belt, between the orbits of Mars and Jupiter. At a mean distance of 3.13 AU from the Sun, it is one of the more populous asteroid families...
of asteroids, which is located in the outer part of the main belt. The family consists of a core of large objects surrounded by a cloud of smaller objects; 24 Themis is a member of the core.
Surface ice
On October 7, 2009, the presence of water iceIce
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
was confirmed on the surface of this asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
using NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
’s Infrared Telescope Facility
Infrared Telescope Facility
The NASA Infrared Telescope Facility is a telescope optimized for use in infrared astronomy and located at the Mauna Kea Observatory in Hawai'i. It was first built to support the Voyager missions and is now the USA national facility for infrared astronomy, providing continued support to...
. The surface of the asteroid appears completely covered in ice. As this ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
layer is sublimated, it may be getting replenished by a reservoir of ice under the surface. Organic compounds were also detected on the surface.
Scientists hypothesize that some of the first water brought to Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
was delivered by asteroid impacts after the collision that produced the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. The presence of ice on 24 Themis supports this theory. Because of its proximity to the sun (~3.2 AU), the widespread ice on the surface of 24 Themis is somewhat unexpected. The surface ice may be replenished by a sub-surface reservoir of water or impact gardening
Impact gardening
Impact gardening is the process by which impact events stir the outermost crusts of moons and other celestial objects with no atmospheres. In the particular case of the Moon, this is more often known as lunar gardening...
—a lunar phenomenon in which the moon overturns surface material at a rate of 1 m/ Gyr.
An alternative mechanism to explain the presence of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
ice on 24 Themis is similar to the hypothesized formation of water on the surface of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
by solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
. Trace amounts of water would be continuously produced by high-energy solar proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s impinging oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
minerals present at the surface of the asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
. The hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
surface groups (S–OH) formed by the collision of protons (H+) with oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atoms present at oxide surface (S=O) can further be converted in water molecules (H2O) adsorbed onto the oxide minerals surface. The chemical rearrangement supposed at the oxide surface could be schematically written as follows:
- 2 S-OH → S=O + S + H2O
or,
- 2 S-OH → S–O–S + H2O
where S represents the oxide surface.
See also
Water presence on other celestial bodies:- CometCometA comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
- Lunar water
- Effect of solar windSolar windThe solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
- Water on Enceladus
- Water on MarsWater on MarsWater on Mars is a psychedelic rock and electronic music group from Quebec City, Québec, Canada. The music trio is led by Philippe Navarro, guitarist, vocalist, arranger, producer, principal lyricist, and music composer....
- Origin of water on EarthOrigin of water on EarthThe question of the origin of water on Earth, or the question of why there is clearly more water on the Earth than on the other planets of the Solar System, has not been clarified...