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...

Vesta’s regolith influences surface features
Posted: 28 March 2012

Bookmark and Share

The Framing Camera aboard NASA’s Dawn spacecraft has been returning some remarkable pictures of Vesta since its arrival at the giant asteroid in July 2011, and some of these were shown at the National Astronomy Meeting in Manchester this week.

Vesta is a differentiated body, which means that as it cooled early in its history, it formed layers and became roughly spherical. It is also covered in a thick layer of loose material known as regolith. Martin Hoffmann from the Max-Planck-Institute for Solar System Research revealed that the mixing of regolith on the surface can make it difficult to decipher the precise thermal evolution of Vesta. “We see some details, but it’s much more complicated to disentangle the effects by the impacts and the early processes by the differentiation that we see.”

An example of a double crater on Vesta. Image: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA.

The regolith on Vesta is much deeper than that of the Moon, and the Dawn scientists can use surface features to estimate this depth of the regolith, as well as see how it varies across the surface.

“If you have regolith which is porous and it’s very deep, then you have compaction patterns outside the impact craters which indicate how deep the regolith can be,” said Hoffman. “In other places these compaction patterns look very shallow, or are not present at all, so in these cases we expect that the regolith is not of that size as we see in other places.”

The thick blanket of porous regolith also means that craters on Vesta can be deeper overall than those on the Moon. This deep regolith has an interesting effect when two objects impact the asteroid at almost the same point on the surface; a double crater can be formed. This is unusual as it was expected that a second impact would destroy the first crater completely.

Hoffmann explained to Astronomy Now how the regolith can become compacted enough to preserve the original crater: “You have some sheet of regolith and then you have the first impact onto this very porous material. This impact causes a compaction pattern in a way that the outer layers are at some distance from the centre where we have most compacted area. Then if you have a later impact on this region this particular compacted area will be laid bare by the subsequent impact, and you can see both the old crater in its remnants where its compacted in parts and the new crater which only removed the surface but not the deeper layers.”

Double craters are a common sight on Vesta. “In many cases we have several of such features in different parts and also the location of where we can find such particular features tells us something about the distribution of the materials on the surface,” said Hoffmann.

Launched on 27 September 2007, Dawn began returning intriguing images of Vesta several months before entering orbit. Initially orbiting high above the asteroid to get a birds eye view, Dawn gradually spiralled down to a lower orbit to image Vesta in breathtaking detail. Once completing its mission at Vesta in July 2012, Dawn will head for spherical asteroid Ceres, where it will arrive in 2015.

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.