Astronomy Now Home
Home Magazine Resources Store

On Sale Now!

The October 2014 issue of Astronomy Now is on sale! Order direct from our store (free 1st class post & to UK addresses). Astronomy Now is the only astronomy magazine specially designed to be read on tablets and phones. Download the app from Google Play Store or the Apple App Store.

Top Stories

Earthshine used to test life detection method
...By imagining the Earth as an exoplanet, scientists observing our planet's reflected light on the Moon with ESO's Very Large Telescope have demonstrated a way to detect life on other worlds...

Solid buckyballs discovered in space
...Astronomers using NASA’s Spitzer Space Telescope have detected a particular type of molecule, given the nickname “buckyball”, in a solid form for the first time...

Steamy water-world gets the Hubble treatment
...Hubble Space Telescope observations of a 7 Earth-mass planet find an unusual water-rich world swathed in a thick, steamy atmosphere...

MESSENGER heads for third Mercury encounter
Posted: September 29, 2009

Bookmark and Share

NASA's MESSENGER spacecraft will make its third and final pass of innermost planet Mercury tonight, on a gravity assist maneuver that will steer it into orbit around the Sun-drenched world in March 2011.

This image was captured yesterday as MESSENGER approaches the rocky planet for the third time. Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

The spacecraft will speed past Mercury's surface at an altitude of 228 kilometres and at over 160,000 kilometres per hour. During this sweeping glance MESSENGER's seven instruments – a camera, a magnetometer, an altimeter and four spectrometers – will capture high resolution colour images and measurements of targets picked out from the previous two flybys. Another five percent of the planet's surface will be imaged for the first time, bringing the mapped area close to one hundred percent.

“We will be pointing at each individual target from several different angles during the flyby, which will allow us to collect more data,” says William McClintock, a MESSENGER mission co-investigator who led the development of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS).

The MASCS team is particularly interested in unusual surface deposits spotted by the camera during MESSENGER’s previous flybys,“One of the big questions planetary scientists have is how much iron there is on Mercury’s surface,” says McClintock. “We hope to pinpoint the iron, determine what chemical form it is in and how it is bound up on the planet’s surface.”

Mercury's core is dominated by iron, which is responsible for maintaining the planet’s magnetic field. The planet's surface is much darker than the Moon’s, indicating that there should be a high iron and/or titanium content. This is thought to be in the form of ilmenite, an iron-titanium oxide, or nanophase iron, which gets distributed on the surface because of space weathering, whereby high energy particles from the solar wind, or micrometeorites, impinge on the planet's surface, changing the optical and physical properties of minerals there.

During tonight's flyby, the area outlined in yellow will be imaged by the Mercury Dual Imaging System (MDIS), and includes never-before-seen terrain of the innermost planet. Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

“We will sample a composition on this side of the planet that could be very different from what we saw on the other side of the planet during the first flyby,” says William Feldman, Co-Investigator for MESSENGER's Neutron Spectrometer. “It would be very surprising if we found the exact same composition that we saw on that first flyby.”

On missions to the Moon and Mars neutron spectrometers have found evidence for the presence of water molecules, and both the Gamma-Ray and Neutron Spectrometer on MESSENGER will search for hydrogen as a possible indicator for water deposits in the cold polar regions of Mercury that never receive full sunlight.

After this third and final flyby MESSENGER will have collected the same amount of data as during a single orbit around Mercury. Once MESSENGER settles into a yearlong pattern of twice daily orbits around Mercury in 2011, analysing the massive streams of images and data “will be like drinking from a fire hose,” says McClintock.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!


© 2014 Pole Star Publications Ltd.