Fast Imaging Plasma Spectrometer


Mission: To provide a comprehensive view of the structure and composition of Mercury from aboard the MESSENGER spacecraft.

Challenge: In order to better understand Mercury’s surface, MESSENGER must gather detailed information about the planet’s magnetic field. 

Solution:  the Fast Imaging Plasma Spectrometer will analyze pickup ions liberated from Mercury’s surface by the solar wind, as well as analyzing the solar winds themselves using imaging mass spectrometry combining a novel wide-angle electrostatic deflection system and a linear time-of-flight system.

Value: FIPS will work as a part of the EPPS instrument to investigate the nature of Mercury’s small, Earth-like magnetosphere and its interaction with the solar wind and Mercury’s thin atmosphere.

Lab: SPRL in collaboration with NASA

Scientific Objective

In 2004 the MESSENGER spacecraft began its seven-year voyage to the planet Mercury. MESSENGER was the first spacecraft to orbit Mercury as well as the first spacecraft to visit Mercury in more than 30 years, following Mariner 10 in 1975. After completing two flybys of Venus and two of Mercury, MESSENGER orbited Mercury for one Earth year, looking for similarities with Venus, Earth, and Mars. 

During these encounters, FIPS measured the expected amounts of ions like sodium, potassium, and calcium that had previously been detected in Mercury’s exosphere. An unusual discovery from this mission, however, was that there was also water present in large quantity. MESSENGER science team member Thomas Zurbuchen, of SPRL, reflected on the surprise of this discovery: “nobody expected that. I don’t know a single person that did. We were astonished, just astonished”.

Several explanations for this discovery have been set forth: First is the theory, founded in Earth-based radar observations, that there may be reservoirs of water ice in small areas of Mercury’s poles trapped in permanently shadowed craters at the poles. Another theory suggests the water could come from comets. Third, the process of chemical sputtering could create water from the ingredients of solar wind and Mercury rock. Though FIPS may have supplied more questions than answers, it is discoveries like these that keep the exploration of space so exciting.


Science team: Thomas Zurbuchen (Instrument Lead), George Gloeckler, Patrick Koehn

Engineering team: Jim Raines (Operations Engineer), Bob Lundgren (System Engineer), Ken Arnett, Curt Cooper, Charles Edmonson, Greg Ritter, Steve Rogacki

Further reading: