As the MESSENGER spacecraft approached Mercury, the UVVS field of view was
scanned across the planet's exospheric "tail," which is produced by the
solar wind pushing Mercury's exosphere (the planet's extremely thin
atmosphere) outward. This figure, recently published in Science magazine,
shows a map of the distribution of sodium atoms as they stream away from
the planet (see PIA10396); red and yellow colors represent a higher
abundance of sodium than darker shades of blue and purple, as shown in the
colored scale bar, which gives the brightness intensity in units of
kiloRayleighs. The escaping atoms eventually form a comet-like tail that
extends in the direction opposite that of the Sun for many planetary
radii. The small squares outlined in black correspond to individual
measurements that were used to create the full map. These measurements are
the highest-spatial-resolution observations ever made of Mercury's tail.
In less than six weeks, on October 6, 2008, similar measurements will be
made during MESSENGER's second flyby of Mercury. Comparing the
measurements from the two flybys will provide an unprecedented look at how
Mercury's dynamic exosphere and tail vary with time.
Date Acquired: January 14, 2008
Instrument: Ultraviolet and Visible Spectrometer (UVVS) of the
Mercury Atmospheric and Surface Composition Spectrometer (MASCS)
These images are from MESSENGER, a NASA Discovery mission to conduct the
first orbital study of the innermost planet, Mercury. For information
regarding the use of images, see the MESSENGER image use policy.
