Mercury's unseen surface revealed by astronomers
BOSTON UNIVERSITY NEWS RELEASE
Posted: May 28, 2000
"More than a quarter-century ago, the Mariner 10 spacecraft flew past Mercury and for the first and only time transmitted satellite-based photos of half of the surface of the planet closest to the Sun," says lead author Jeffrey Baumgardner, senior research associate in the Center for Space Physics at BU. "Capturing similar images from a ground-based telescope represents a significant milestone in advanced instrumentation," he adds.
The BU images, taken on August 29, 1998, at the Mt. Wilson Observatory in California, reveal surface markings similar to the bright craters and dark lunar mare found on the Moon. The BU images captured using a digital camera and stored on CD-ROMs for subsequent processing show never-before- seen-portions of Mercury.
Photographing Mercury is challenging because of the planet's proximity to the Sun. Mercury only has a few viewing times, before sunrise or shortly after sunset. At rare times when 'the seeing' is right, the air is clear and researchers are looking through less turbulence in Earth's atmosphere. Opportunities to photograph Mercury from space are also limited because light sensitive equipment, such as the Hubble Space Telescope, are not allowed to look at objects close to the Sun, such as Mercury or Venus. This restriction has been established to avoid the possibility of an accidental pointing error causing too much light to fall upon an instrument.
"The observations were made shortly after sunrise before the Sun's heating of the atmosphere distorted the images captured by the telescope," says Michael Mendillo, professor of astronomy at BU.
Baumgardner and Research Associate Jody Wilson assisted by Mead Misic, a sophomore in the College of Engineering, all took part in the search for the perfect images. They developed sophisticated computer techniques to identify the best images with detail taken during rare instances of 'perfect seeing.'
"We captured multiple images of Mercury during these rare instances of 'perfect seeing,'" says Wilson. "and by combining these images, a unique photograph with details and clarity resulted. "
The Boston University team plans to make additional observations of Mercury this fall, even pushing the technique to try to image the planet's weak atmosphere. "Mercury has a thin atmosphere created by the ejection of atoms from its surface, a process that also occurs on our Moon," Mendillo explained. One of the chemical elements in Mercury's atmosphere is sodium, a gas somewhat easy to detect because it reflects sunlight very efficiently. "We hope to try our first sodium detection experiments this fall," Baumgardner said. "But that will first involve building a more sensitive detector system."