NASA's Mars Exploration Rover Spirit continues to take advantage of extra
solar energy by occasionally turning its cameras upward for night sky
observations. Most recently, Spirit made a series of observations of
bright star fields from the summit of "Husband Hill" in Gusev Crater on
Mars. Scientists use the images to assess the cameras' sensitivity and to
search for evidence of nighttime clouds or haze. The image on the left is
a computer simulation of the stars in the constellation Orion. The next
three images are actual views of Orion captured with Spirit's panoramic
camera during exposures of 10, 30, and 60 seconds.
Because Spirit is in the southern hemisphere of Mars, Orion appears upside
down compared to how it would appear to viewers in the Northern Hemisphere
of Earth. "Star trails" in the longer exposures are a result of the
planet's rotation. The faintest stars visible in the 60-second exposure
are about as bright as the faintest stars visible with the naked eye from
Earth (about magnitude 6 in astronomical terms). The Orion Nebula, famous
as a nursery of newly forming stars, is also visible in these images.
Bright streaks in some parts of the images aren't stars or meteors or
unidentified flying objects, but are caused by solar and galactic cosmic
rays striking the camera's detector.
Spirit acquired these images with the panoramic camera on Martian day, or
sol, 632 (Oct. 13, 2005) at around 45 minutes past midnight local time,
using the camera's broadband filter (wavelengths of 739 nanometers plus
or minus 338 nanometers).
