After almost 33 years, NASA has returned to the planet Mercury through the aid of the MESSENGER spacecraft. MESSENGER, which stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging, made its first flyby on Jan. 14, 2008 at 2:04 p.m. EST, passing within 200 kilometres of the surface.
The last spacecraft to visit Mercury was the Mariner 10, which made three flybys from 1974 to 1975. However, it was only able to photograph 45 per cent of the surface, as the same hemisphere was lit during each of its passes. Even so, the photographs and information uncovered by Mariner 10 were enough to pique the interest of scientists.
MESSENGER has already sent back many highresolution images of the first planet from the sun, including photos of the hemisphere not seen in the mid-1970s. The spacecraft is equipped with wide and narrow angle colour and monochrome cameras. Better known as the Mercury Dual Imaging System (MDIS) instrument, the images of the hemisphere show it to be heavily cratered, much like Earth’s moon, revealing ridges, cliffs and evidence of volcanic activity. Planetary geologists study the high-resolution close-ups to understand how Mercury’s surface has evolved over the last four billion years. The MESSENGER mission aims to answer questions about the structure of Mercury’s core, the nature of its magnetic field, and the reason behind its unusual density.
A major point of interest for NASA scientists is Mercury’s Caloris basin, one of the largest in the solar system. Mariner 10 saw less than half of it, but the MESSENGER has already photographed what its predecessor could not. “Caloris is huge, about a quarter of the diameter of Mercury, with rings of mountains within it that are up to three kilometres high,” said Dr. Louise M. Prockter, instrumental scientist for the Mercury Dual Imaging System, and a scientist at the Johns Hopkins University Applied Physics Laboratory. “By looking through different colour filters, we can start to understand what the composition of the Caloris basin may be and learn something about the subsurface of Mercury.”
Even with massive amounts of data to sift through, the spirits of NASA scientists involved with the project are high.
“I’ve been waiting for this for 38 years—since my parents woke me up at age 18 months to watch the first Apollo moon landing on our black-and-white TV,” wrote MESSENGER instrumental scientist Noam Izenberg. “Today I joined a small crowd of scientists and engineers in the MESSENGER Science Operation Center, and watched the first picture of Mercury in 33 years—showing almost a third of the planet that had never been seen in any detail before—pop up, BLAM, on a screen in all of its alien glory.”
NASA scientists aren’t the only ones impressed by the new photos of Mercury. “Even though the pictures reveal, to our eyes, another uninteresting, barren planet in our solar system, they also confirm the high value of our little unique and beautiful planet in the cosmic shore,” said Siavash Ganjbakhsh, a fourth-year evolutionary biology student and member of the Astronomy and Space Exploration Society. “We ought to protect and appreciate this beauty.”
MESSENGER will make two more Mercury flybys— one later this year and one in 2009 —before settling into orbit around the planet in 2011.
