In a groundbreaking discovery for Mercury science, the MESSENGER spacecraft imaged a plume of material erupting from the surface of the innermost planet. In an MDIS image taken early this morning, a bright source of light may be seen above Mercury's southern hemisphere. Located at approximately 67°S, 55°E, close to the newly named Alver basin, this light source appears to be

MESSENGER team members are currently analyzing images of the eruption. One hypothesis under consideration is that the brightness indicates the presence of a "fire fountain," an eruption during which lava is ejected from depth in a jet-like spray of molten rock. There also appears to be a dimmer cloud of material above the central plume. Under the fire fountain hypothesis, this higher cloud may be composed of smaller droplets of lava of a size that allows them to be blasted to greater altitudes. Most of these droplets will probably fall back to the surface, producing a distinctive "pyroclastic halo" around the vent like those seen elsewhere on Mercury.

An alternative possibility is that the plume is a "geyser" of volatile materials, analogous to the plume at Saturn's moon Enceladus. Under this scenario, a pocket of volatile-rich material may have been heated by the intrusion of subsurface magma, solar tidal dissipation, or some other process, fueling a geyser-like eruption at the surface. Because of the recent identification of water ice at Mercury's poles, the MESSENGER team is pursuing the idea that water may be involved in the eruption. Given that possibility and the date of the discovery, the team has already proposed to the International Astronomical Union that the feature be given the name "Poisson d'Avril."

Scientists will continue to acquire and examine as many images of the eruption as possible. The MESSENGER spacecraft has been conducting orbital operations at Mercury for two years, first during its primary mission and then during a year-long extended mission. The MESSENGER team recently submitted a proposal to NASA to extend the mission further by an additional two years of orbital operations.

Date acquired: April 1, 2013
Image Mission Elapsed Time (MET): 6607500
Image ID: 3763800
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (749 nanometers)
Center Latitude: -83.1°
Center Longitude: 262.7° E
Resolution: The resolution near the center of the image is approximately 2 km (1.25 mi.) per pixel
Scale: Mercury's radius is 2,440 kilometers (1,520 miles)

The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System's innermost planet. MESSENGER acquired over 150,000 images and extensive other data sets. MESSENGER is capable of continuing orbital operations until early 2015.

For information regarding the use of images, see the MESSENGER image use policy.