Solar System: Inner Planets - Mercury
The Fastest Planet
Mercury, a terrestrial planet and the innermost planet in the solar
system, has temperatures that are the most extreme in the solar
system. On the day side of Mercury, the thermometer reaches 700
K (800°F/427°C). When night falls, temperatures plunge to
just 90 K (-298°F/-183°C).
Most of what we know about Mercury we learned from three Mariner
10 spacecraft flybys in 1974 and 1975. During those flybys, Mariner
10 mapped nearly 45 percent of Mercurys surface and gathered
data about the planets atmosphere, temperature, geology, and
more. Images from the probe revealed a crater-pocked planet that
looks a lot like our Moon. The data from Mariner 10 are still being
analyzed by scientists and have actually raised many questions,
such as: Is there ice at Mercurys poles? Why is Mercury so
dense? Whats inside the planets core? Scientists have
many different theories that attempt to answer these questions.
Perhaps some of them will be answered during the next mission to
Courtesy of NASA JPL
| In 2004, a spacecraft called MESSENGER
(for MErcury Surface, Space ENvironment, GEochemistry, and Ranging)
will be launched on a five-year journey across the inner solar system
to Mercury. During its mission, MESSENGER will fly past Mercury twice
(in 2007 and 2008), taking pictures and gathering data. In 2009, MESSENGER
will begin a one-year orbit of Mercury, collecting data and pictures
of the entire planet.
Because it appears to us that Mercury is never more than 28 degrees
away from the Sun, its hard for us to see the planet except
occasionally at either sunrise or sunset.
In 2004, Mercury is best seen in the early evening in late March
through April, July, and November. In July and August, you can see
Mercury and Mars together in the evening sky.