Messenger Spacecraft to Photograph Mercury Scientists working on the NASA mission to Mercury will get a bit of holiday cheer on Monday, as the agencys Messenger spacecraft speeds toward its third encounter with the planet and snaps about 1,500 pictures.
"A planetary flyby is very much like Christmas morning to the science team" - Sean C. Solomon, a scientist at the Carnegie Institution of Washington and the principal investigator of the mission.
In 2004, NASA launched a spacecraft called MESSENGER to Mercury. After two successful flybys in 2008, the space probe is scheduled to fly by the diminutive world again on Wednesday.
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to confer the name of Lebanese poet Gibran Khalil Gibran on an impact crater on Mercury. The Gibran crater and 15 other newly named craters were imaged during the mission's first two flybys of Mercury in January and October last year.
As the closest planet to the sun, Mercury is scorching hot, with daytime temperatures of more than 800 degrees Fahrenheit (approximately 450 degrees Celsius). It is also the smallest rocky planet, so its gravity is weak, only about 38 percent of Earth's. These conditions make it hard for the planet to hold on to its atmosphere, which is extremely thin, and invisible to the human eye. However, it can be seen by special instruments attached to telescopes and spacecraft like MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging).
"Mercury's atmosphere is so thin, it would have vanished long ago unless something was replenishing it" - Dr. James A. Slavin of NASA's Goddard Space Flight Centre, Greenbelt, Md., a co-investigator on NASA's MESSENGER mission to Mercury.
That something could be the solar wind, a thin gas of electrically charged particles, called a plasma, which blows constantly from the surface of the sun. The solar wind moves quickly, usually around 400 to 600 kilometres/second; fast enough to blast atoms off the surface of Mercury. Through a process called "sputtering," solar wind particles that crash into Mercurys surface transfer sufficient energy to launch some atoms into ballistic trajectories high above the surface and replenish Mercury's atmosphere, according to Slavin.
The main surface feature seen is impact craters. Most billions of years old, caused by the impact of Asteroids and Comets at the end of the late heavy bombardment, (Final stage of main solar system formation). And it is one of these impact craters that holds the title of largest crater in the solar system. It is called the Caloris Basin and has as a diameter of over 1500Km! So large was this impact that it forced up the surrounding are to form a mountain range 2 Km high. Other crater features on Mercury are called chain cratering. Chain cratering is formed when a planets gravity rips apart an object say an Asteroid or comet, and the subsequent fragments impact the planet or it's moon, like a chain of bullets from a machine gun.
Data sent back to Earth by NASAs Messenger spacecraft have given scientists at the University of Colorado another puzzling glimpse at the planet Mercury, one of the least-studied planets in the solar system. Boulder astronomers discovered surprising amounts of magnesium clumped in the planets thin atmosphere.
A bizarre spoke-like pattern of troughs and ridges has been found on the surface of Mercury by NASA's Messenger spacecraft. The feature is unlike any to be found in basins on Mercury or elsewhere in the solar system. The feature sits in the Rembrandt impact basin, the second-largest impact scar on the planet.
Until recently, the layers of rock forming Mercury's crust were thought to be a lot like those of the Moon: cold, dead and full of the bright minerals found in the Earth-facing lunar highlands. But after two visits from the Messenger spacecraft, the planet is looking less like the Moon and more like a place that has been ripped by fault-grinding tremors and pierced by planet-surfacing bouts of volcanic eruption - things associated with the bigger boys of the inner solar system. Mercury, it seems, can punch above its weight.
Researchers on the MESSENGER team today published a suite of findings from the October flyby in the journal Science. Among the discoveries: a massive impact crater dubbed Rembrandt, which spans some 700 kilometres, covering an area comparable to the U.S.
MESSENGER Spacecraft Reveals A Very Dynamic Planet Mercury A NASA spacecraft gliding over the surface of Mercury has revealed that the planet's atmosphere, the interaction of its surrounding magnetic field with the solar wind, and its geological past display greater levels of activity than scientists first suspected. The probe also discovered a previously unknown large impact basin about 430 miles in diameter -- equal to the distance between Washington and Boston. Analyses of these new findings and more are reported in four papers published in the May 1 issue of Science magazine.
Mercury was once seen as a cold, dead little world, spinning around the sun unchanged for the past 4 billion years. No longer: Observations from the Messenger spacecraft say it's anything but. NASA's orbiter is sending back evidence of massive volcanism, strange impact craters and magnetic tornadoes that funnel plasma directly from the sun to the planet's surface.
"It's definitely not this picture of an ancient world where everything that happened to it happened billions of years ago and nothing happened since then. We're seeing a very dynamic planet that has a lot going on today" - Tom Watters of the Smithsonian Institution in Washington, DC.