NASA’s MESSENGER spacecraft is only the second spacecraft to successfully reach orbit around the tiny planet Mercury, the closest planet to the sun. MESSENGER arrived at its destination in March 2001, and after spending a year and a half probing the little planet, the orbiter sent back some startling information. It seems our neighbor may be an alien.
By the way, MESSENGER stands for MErcury Surface, Space ENvironment, Geochemistry, and Ranging. Someone must have stayed up very late indeed to come up with that acronym. It was designed to investigate the planet’s composition and magnetic field, what materials could be found at the poles, and the structure of the little planet’s core.
X-ray spectrometer readings show that Mercury has high levels of magnesium and sulfur on its surface, which is quite different from the other planets in the solar system. For example, the concentration of sulfur found on the surface is about ten times as much as that found on Earth. Its northern volcanic plains formed through upwellings of rocks that are unique to Mercury, with higher ratios of magnesium to silicon, sulfur to silicon, and calcium to silicon, but with lower ratios of aluminum to silicon.
Mercury is also the second densest planet after earth. It has a huge iron core that makes up approximately 75% of the planet’s radius, or about 1,100 to 1,200 miles (1,800 to 1,900 km). Its mantle is believed to be about 300 miles thick.
Despite its surface temperature, which can reach up to 800 degrees Fahrenheit, astronomers discovered in 1991 that Mercury may have water at its north and south poles inside perpetually cold craters. Did the planet originally have its own water, or did falling comets or meteoritesbring ice to the planet?
So if Mercury’s basic composition is so different from those of the other planets in the solar system, where might it have come from? Was it a wanderer that came too close to the sun and was captured How did it manage to wind its way through the rest of the planets and the asteroid belt without hitting anything? These questions, among others, are bound to keep astronomers busy for the next several years.
For more information about the peculiar story of this “alien” planet, visit here
If you’re interested in learning more about Mercury, National Geographic has posted a very detailed article here