4,878km (3,032 miles) at its equator, which is
about two-fifths of Earth's diameter.
* Temperature: ?
* Orbit: 57,910,000 km (0.38 AU) from Sun. Orbiting the Sun once every 88 days.
* Average Distance: About 58 million km (36 million miles)
* Time to Rotate: 58.6 days
* Mass: 3.30e23 kg (5.5% of Earth's)
* Moons: 0
* Period of Rotation: 58.6462 days.
Mercury has a very elliptical (oval-shaped) orbit. At perihelion (at its closest
point) it is about 46 million km (28.58 million miles) from the Sun, but at
aphelion (at its farthest point) it is 70 million km. Mercury is about 77.3
million km (48 million miles) from Earth at its closest approach. Mercury is not
easily seen from Earth due to its small angular separation from the Sun. Mercury
moves around the sun faster than any other planet. Mercury travels about 48 km
(30 miles) per second and it takes 88 Earth days to orbit the sun. The Earth
goes around the sun once every 365 days (one year).
The planet rotates once about every 59 Earth days, a rotation slower than that
of any other planet except Venus. As a result of the planet's slow rotation on
its axis and rapid movement around the sun, a day on Mercury lasts 176 Earth
days (interval between one sunrise and the next).
Mercury is the second densest major body in the solar system after Planet Earth
and its density is slightly less than the Earths. Mercury's smaller mass makes
its force of gravity only about a third as strong as that of the Earth. An
object that weighs 100 pounds on the Earth would weigh only about 38 pounds on
Mercury has a large iron core which is most likely at least partially molten and
generates a magnetic field about 1% as strong as that of Earth's. Mercury's
interior appears to resemble that of the Earth. Both planets have a rocky layer
called a mantle beneath their crust and both planets have an iron core.
The surface of Mercury consists of cratered terrain and smooth plains and many
deep craters similar to those on the moon. The craters formed when meteors or
small comets crashed into the planet. The largest known crater is Caloris Basin,
with a diameter of 1300 km (800 miles).
the other terrestrial planets (Venus, Earth and Mars) Mercury is made mostly of
rock and metal. Mercury's surface appears to be much like that of the moon. It
reflects approximately 6 percent of the sunlight it receives, about the same as
the moon's surface reflects. Like the moon, Mercury is covered by a thin layer
of minerals called silicates in the form of tiny particles.
of Mercury made by Earth-based radar indicate that craters at Mercury's poles
contain water ice. The floors of the craters are permanently shielded from
sunlight, so the temperature never gets high enough to melt the ice.
Mercury is a planet of extreme temperature variations. It is hotter on Venus,
but with less fluctuations. The temperature on the planet may reach 450 degrees
C (840 degrees F) during the day. But at night, the temperature may drop as low
as -170 degrees C (-275 degrees F). The sunlight on Mercury’s surface is 6.5
times as intense as it is on Earth due its closeness to the sun.
Mercury is dry, extremely hot and almost airless. Planet Mercury is too small
for its gravity to retain any significant atmosphere over long periods of time.
The weak atmosphere contains hydrogen, helium, oxygen, sodium, calcium and
to the heat of the planet, the very thin atmosphere is blasted off its surface
by the solar wind and quickly escapes into space. Mercury's atmosphere is
constantly being replenished.
Mercury does not have enough atmosphere to slow down meteoroids and burn them up
by friction. The sun's rays are approximately seven times as strong on Mercury
as they are on the Earth. The sun also appears about 2 1/2 times as large in
Mercury's sky as in the Earth's.
Greeks gave it two names: Apollo for when it appeared as a morning star and
Hermes when it came as an evening star.
Roman mythology Mercury is the god of commerce, travel and thievery, the Roman
counterpart of the Greek god Hermes, the messenger of the Gods. The planet
probably received this name because it moves so quickly across the sky
plant and animal life of the Earth could not live on Mercury because of the lack
of oxygen and the intense heat. Scientists doubt that the planet has any form of
Because of Mercury's size and nearness to the sun, the planet is often hard to
see from the Earth without a telescope. At certain times of the year, Mercury
can be seen low in the western sky just after sunset. At other times, it can be
seen low in the eastern sky just before sunrise.
When viewed through a telescope, Mercury can be seen going through ‘changes’ in
shape and size. These apparent changes are called phases and resemble those of
the moon. They result from different parts of Mercury's sunlit side being
visible from the Earth at different times.
Mercury has been known since ancient times. Until the mid-1960's, astronomers
believed that Mercury rotated once every 88 Earth days, the same time the planet
takes to go around the sun. If Mercury did this, one side of the planet would
always face the sun and the other side would always be dark. However, radar
studies conducted in 1965 showed that the planet rotates once in about 59 days.
only spacecraft to come close to Mercury was Mariner 10 from 1974 to 1975, which
was only able to map 40%–45% of the planet's surface.
Planet Mercury was explored in three flybys by the
Mariner 10 spacecraft in 1974 and 1975.
In the future, NASA is planning to
explore Mercury with the MESSENGER Spacecraft and Europe/Japan with BepiColombo.R
Messenger Spacecraft: In 2004, the United States launched the Messenger probe to Mercury. Messenger
was scheduled to fly by Mercury twice in 2008 and once in 2009 before going into
orbit around the planet in 2011. The probe was then to orbit Mercury for one
Earth year while mapping Mercury's surface and studying its composition,
interior structure, and magnetic field.
A second NASA mission to Mercury, named MESSENGER (MErcury Surface, Space
ENvironment, GEochemistry, and Ranging), was launched on August 3, 2004, from
the Cape Canaveral Air Force Station aboard a Boeing Delta 2 rocket. The
MESSENGER spacecraft will make several close approaches to planets to place it
onto the correct trajectory to reach an orbit around Mercury. It made a fly-by
of the Earth in August 2005, and of Venus in October 2006 and June 2007. Three
fly-bys of Mercury are scheduled, in January 2008, October 2008, and September
2009. The probe will then enter orbit around the planet in March 2011.
BepiColombo: Japan is planning a joint mission with the European Space Agency called
BepiColombo, which will orbit Mercury with two probes: one to map the planet and
the other to study its magnetosphere. An original plan to include a lander has
been shelved. Russian Soyuz rockets will launch the probes in 2014. As with
MESSENGER, the BepiColombo probes will make close approaches to other planets en
route to Mercury, passing the Moon and Venus and making several approaches to
Mercury before entering orbit. The probes will reach Mercury in about 2019,
orbiting and charting its surface and magnetosphere for a year.
The probes will carry a similar array of spectrometers to those on MESSENGER,
and will study the planet at many different wavelengths including infrared,
ultraviolet, X-ray and gamma ray. Apart from intensively studying the planet
itself, mission planners also hope to use the probe’s proximity to the Sun to
test the predictions of General Relativity theory with improved accuracy.
The mission is named after
Giuseppe (Bepi) Colombo, the scientist who first
determined the nature of Mercury’s orbital resonance with the Sun and who was
also involved in the planning of Mariner 10’s gravity-assisted trajectory to the
planet in 1974.
Mercury has been suggested as one possible target for space colonization of
the inner solar system, along with Mars, Venus, the Moon and the asteroid belt.
Permanent colonies would almost certainly be restricted to the polar regions due
to the extreme daytime temperatures elsewhere on the planet, although excursions
to the other parts of the planet would be feasible with appropriate measures
More Facts on Planet Mercury - Did you know?
Mercury is the fastest moving planet in our Solar System and is the nearest
planet to the Sun. Mercury is one of the four terrestrial planets, being a rocky body like the
Earth. It is the smallest of the four.
How big is the planet mercury?
When was planet mercury discovered? Unknown
Color of planet mercury? Orangery
Mercury orbits the sun at an average distance of about 36 million miles (58
million kilometres), compared with about 93 million miles (150 million
kilometres) for Earth.
is only 4,878km across and is not much larger than our moon. Its surface
temperature ranges from
-170 degrees at night to 350 degrees in the day. The
largest feature on Mercury is the Caloris Basin.