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First Mercury Flyby

January 14, 2008

Speaker: Marilyn Lindstrom Program Scientist, NASA Headquarters

NASA Museum Alliance Embargoed until 1 pm 1/30/08

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Mercury the Mystery Planet

• Least known terrestrial planet

• Mariner 10 only spacecraft– 3 flybys 1974-1975– Imaged just 45% of planet

– Large core– Small magnetic field

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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

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Science Questions

• Why is Mercury so dense?

• What is the geologic history of Mercury?

• What is the nature of Mercury’s magnetic field?

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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?

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Science Instruments

MDIS - dual imaging spectrometer, MASCS - UV-VIS-IR spectrometer, MLA - laser altimeter, MAG - magnetometerEPPS - energetic particles & plasma spectrometer, GRNS – gamma ray & neutron spectrometer, XRS - X-ray spectrometer

radio science uses Doppler on communications tracking

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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)

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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.

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Launch

Launched August 3, 2004 aboard a three-stage Boeing Delta II rocket!

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Flyby Plan

Messenger approached in nightime on the Mariner 10 side and departed in daytime on the newly seen MESSENGER side.

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MOC and SOC

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First Image Unseen Side

First Look on Jan. 14, 2008 at Mercury’s Previously Unseen Side

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Geology - Craters

Most crater ejects is closer to the rim than on the moon due to higher gravity.

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Geology – Basins

Multi-ring basin

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Geology – Scarps

Scarps (cliffs) can be hundreds of Km long; the scarp in this image is 200 Km (125 miles) wide.

Scarp

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Geology - Poles

North pole South pole

The south pole is more heavily cratered than the north pole.

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Geology - History

Craters

Plains

ScarpsSecondaryCraters

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Full Color Image

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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.

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Geophysics

•Laser Altimetry (MLA)

•Two craters are easily visible

•Magnetic Field•Internal, dipolar

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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.

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Atmosphere

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) found Sodium and Hydrogen tails that extend out 15,000 miles.

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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.

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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.

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Spider Radial Grabens

Radial graben “Spider” near center of Caloris basin is unique on Mercury, unseen on Moon or Mars

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We’ll be back!

The next flyby will occur October 6, 2008.

Orbit insertion will occur March 18, 2011.