• Introduction
    • Strofio



      Strofio is a unique mass spectrometer that is part of the SERENA suite of instruments that will fly on board the European Space Agency’s BepiColombo/Mercury Planetary Orbiter (MPO) spacecraft. Strofio will determine the chemical composition of Mercury’s surface, providing a powerful tool to study the planet’s geological history.

      The SERENA instruments include two Neutral Particle Analyzers (Strofio and ELENA) and two Ion Spectrometers (MIPA and PICAM). Together they will investigate the complex particle environment that surrounds Mercury called the “exosphere.” The exosphere is different from an atmosphere. In an atmosphere the molecules constantly collide and change their velocity. In the collision-free exosphere, the particles move due to gravity and, if present, sunlight pressure. Particles escape from Mercury’s surface and flow out into the exosphere, then either return to the surface or are lost in planetary space.


      Mission Management

      Dr. Stefano Livi
      Dr. Stefano Livi
      Principal Investigator

      Dr. Stefano Livi of Southwest Research Institute (SWRI) in San Antonio, TX, is the Principal Investigator. Project management and instrument development are being performed at SWRI.

  • Science Objectives
    • Strofio will provide answers to these scientific questions:

      What is the composition of Mercury's exosphere?

      How do Mercury's exosphere and magnetosphere interact?

      How do Mercury's exosphere and surface interact?

      What is the composition of Mercury's surface?

      NASA's Strofio instrument will investigate the composition of Mercury's surface and its exosphere.
      NASA's Strofio instrument will investigate the composition of Mercury's surface and its exosphere. Mercury’s mass is just 5-1/2 percent that of Earth.
  • Details

      The current plan is for the BepiColombo mission to launch in August 2015 and arrive at Mercury in 2022 for a year-long orbit. It will launch from Kourou, French Guiana, in South America, the location of France and ESA’s main spaceport. The launch vehicle will be an upgraded Soyuz-2B rocket with a Fregat M upper stage. Plans call for an early lunar gravity assist, then an interplanetary cruise phase of nearly six years that includes a series of five planetary flybys (Earth, Venus 2x, Mercury 2x) to reach the innermost planet.

      The mission consists of two separate spacecraft: the Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter. Together they will study the origin and evolution of a planet that is close to its parent star by examining Mercury’s form, interior structure, geology, composition and craters; the composition and dynamics of Mercury’s exosphere; the structure and dynamics of its magnetosphere; the origin of its magnetic field; and the origin and composition of its polar deposits.


      Artist depiction of the two BepiColombo spacecraft, the Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter, in their elliptical polar orbits around Mercury.
  • Noteworthy
    • Seven chemicals have been identified on Mercury through measurements from ground-based instruments and from the Mariner 10 and MESSENGER spacecraft. These seven elements - hydrogen, helium, oxygen, sodium, potassium, calcium and magnesium – account for only 20-30% of the observed total pressure inferred from radio occultation measurements. Strofio is part of a mission doing detective work to learn what makes up the other 70%.

      An image of the planet Mercury
      An image of the planet Mercury, made during the January 2008 flyby of the planet by MESSENGER.