1/30/20081 MESSENGER First Mercury Flyby First Mercury Flyby January 14, 2008 Speaker: Marilyn Lindstrom Program Scientist, NASA Headquarters NASA Museum Alliance Embargoed until 1 pm 1/30/08

1/30/20082 MESSENGER First Mercury Flyby Mercury the Mystery Planet Least known terrestrial planet Mariner 10 only spacecraft –3 flybys –Imaged just 45% of planet –Large core –Small magnetic field

1/30/20083 MESSENGER First Mercury Flyby MESSENGER the Mercury Orbiter Principal Investigator: Sean Solomon, Carnegie Institution of Washington (CIW) Project Manager: Peter Bedini Johns Hopkins University Applied Physics Laboratory (APL) Mission design, spacecraft development, and operations - APL Instruments provided by APL, NASA GSFC, U. Colorado, U. Michigan

1/30/20084 MESSENGER First Mercury Flyby Science Questions Why is Mercury so dense? What is the geologic history of Mercury? What is the nature of Mercury’s magnetic field?

1/30/20085 MESSENGER First Mercury Flyby Science Questions What is the structure of Mercury’s core? What are the unusual materials at Mercury’s poles? What volatiles are important at Mercury?

1/30/20086 MESSENGER First Mercury Flyby Science Instruments MDIS - dual imaging spectrometer, MASCS - UV-VIS- IR spectrometer, MLA - laser altimeter, MAG - magnetometer EPPS - energetic particles & plasma spectrometer, GRNS – gamma ray & neutron spectrometer, XRS - X-ray spectrometer radio science uses Doppler on communications tracking

1/30/20087 MESSENGER First Mercury Flyby Spacecraft Lightweight body Large fuel tank (half the mass is fuel) Several types of thrusters (bipropellant & hydrazine) Ceramic fabric sunshade Adjustable solar panels Redundant systems (PSE,DPU)

1/30/20088 MESSENGER First Mercury Flyby Trajectory 6 planetary flybys provide gravity assists to get into Mercury orbit (1 Earth, 2 Venus, 3 Mercury) We are about half-way there. 5 major propulsive maneuvers (and many minor ones) provide the thrust and guidance.

1/30/20089 MESSENGER First Mercury Flyby Launch Launched August 3, 2004 aboard a three-stage Boeing Delta II rocket!

1/30/ MESSENGER First Mercury Flyby Flyby Plan Messenger approached in nightime on the Mariner 10 side and departed in daytime on the newly seen MESSENGER side.

1/30/ MESSENGER First Mercury Flyby MOC and SOC

1/30/ MESSENGER First Mercury Flyby First Image Unseen Side First Look on Jan. 14, 2008 at Mercury’s Previously Unseen Side

1/30/ MESSENGER First Mercury Flyby Geology - Craters Most crater ejects is closer to the rim than on the moon due to higher gravity.

1/30/ MESSENGER First Mercury Flyby Geology – Basins Multi-ring basin

1/30/ MESSENGER First Mercury Flyby Geology – Scarps Scarps (cliffs) can be hundreds of Km long; the scarp in this image is 200 Km (125 miles) wide. Scarp

1/30/ MESSENGER First Mercury Flyby Geology - Poles North pole South pole The south pole is more heavily cratered than the north pole.

1/30/ MESSENGER First Mercury Flyby Geology - History Craters Plains Scarps Secondary Craters

1/30/ MESSENGER First Mercury Flyby Full Color Image

1/30/ MESSENGER First Mercury Flyby Geochemistry The Mercury spectrum shows the degree to which different wavelengths of sunlight are absorbed or reflected by its surface materials. Dips in the spectrum indicate where sunlight shining on the surface is partially absorbed.

1/30/ MESSENGER First Mercury Flyby Geophysics Laser Altimetry (MLA) Two craters are easily visible Magnetic Field Internal, dipolar

1/30/ MESSENGER First Mercury Flyby Magnetosphere This plot shows the measured magnitude of the magnetic field of Mercury as MESSENGER executed its first flyby of that planet. MESSENGER’s Magnetometer (MAG) provided definitive identification of all boundaries of the Mercury magnetosphere system and revealed a less active system than was seen during the first Mariner 10 flyby.

1/30/ MESSENGER First Mercury Flyby Atmosphere The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) found Sodium and Hydrogen tails that extend out 15,000 miles.

1/30/ MESSENGER First Mercury Flyby Caloris Basin Caloris basin is bigger and more complex than we thought: Mariner 10 saw less than ¼ of this basin that is one of the largest in the solar system. The estimated diameter has increased to 1550 km.

1/30/ MESSENGER First Mercury Flyby Caloris Basin Craters inside the basin include bright ray craters, a multi-ring basin, bright floored craters and dark halo craters. The surface on the interior is lighter color than that on the outside, indicating a difference in composition.

1/30/ MESSENGER First Mercury Flyby Spider Radial Grabens Radial graben “Spider” near center of Caloris basin is unique on Mercury, unseen on Moon or Mars

1/30/ MESSENGER First Mercury Flyby We’ll be back! The next flyby will occur October 6, Orbit insertion will occur March 18, 2011.