ESA SMART-1: Revealing unknown regions of the moon

Credit: ESA/SMART-1 /AMIE camera team/Space Exploration Institute

The greyscale pattern of dark and light blotches on the Moon is a familiar sight to stargazers.

However, there are regions that remained relatively mysterious to us until surprisingly recently, most notably the Moon's polar regions, which astronomers have dubbed 'Luna Incognita', or 'the unknown Moon'.

In recent years, missions including ESA SMART-1 have shed light on these regions of the lunar surface, and they are now better known.

This mosaic covers about 700 km by 220 km and was taken by the Advanced Moon Imaging Experiment on SMART-1.

It shows a trio of craters very near to the Moon's north pole, on the edge of the Luna Incognita. From right to left, these craters are named Plaskett, Rozhdestvenskiy and Hermite.

Hermite (104 km diameter) is perched right on the edge of the Moon's northern limb, while Plaskett (109 km diameter) and Rozhdestvenskiy (177 km diameter) overlap the lunar far side.

Lunar South Pole image by ESA SMART-1. 

Credit: ESA

We only ever see the same hemisphere of the Moon due to 'tidal locking' – this causes the Moon to orbit Earth once in the same time it takes to spin once about its axis.

However, we actually see around 59% of the lunar surface owing to factors such as the eccentricity of the Moon's orbit, its orientation with respect to Earth, and the rotation of Earth.

Over time, these little variations add up and the Moon appears to oscillate slowly, allowing us to peer a bit further around the lunar surface at its edges. This effect is known as libration.

Plaskett's location is within one of the zones that seems to oscillate. For just a few days during a few months each year, Earth can be seen from Plaskett's northern rim, one of the key reasons it may make a suitable lunar outpost for simulating a mission to Mars.

This infrequent contact would be ideal to test how astronauts cope with being isolated from Earth, without requiring the additional separation or risk involved in actually travelling to the Red

ESA SMART-1 Lunar Image: Messy peaks of Zucchius

Credit: ESA /SMART-1 /AMIE camera team/ Space Exploration Institute

Even to the naked eye, our Moon looks heavily cratered.

The snippet of carved and pitted lunar surface shown in this image lies within a 66 km-wide crater known as Zucchius.

From our perspective, Zucchius is located on the edge of the southwest limb of the Moon.

AMIE camera

The crater's uneven and messy appearance is a result of how it formed. Lunar craters like Zucchius were created when rocky bodies, such as, meteors and asteroids, collided with the Moon at speeds of tens of kilometres per second, smashing holes into its surface.

More forceful impacts caused material to spring back upwards, a bit like a water droplet hitting a body of water.

This process formed a peak in the centre of the impact crater, as shown here by the cluster of bobbly mounds.

Zucchius's central peak and other features are quite well preserved. They are thought to have formed in the last 1.2 billion years, a time dubbed the 'Copernican period'.

This is very recent compared to the Moon's age of 4.4 billion years.

Earth was also cratered in this way, were it not for our planet's different conditions it would look a lot like the Moon.

Plate tectonics, the atmosphere and the presence of liquid water have all contributed to changing the shape and appearance of Earth's surface over time, eroding, covering and smoothing away surface blemishes.

This image was taken with the Advanced Moon Imaging Experiment on board ESA's SMART-1 on 14 January 2006, as the spacecraft skimmed just 753 km above the Moon's surface.

Zucchius was named after the 17th-century Italian astronomer Niccolò Zucchi, who was involved in some of the first designs for the reflecting telescope, and who made early observations of Jupiter's belts and spots on Mars.

ESA SMART-1 Image: A peppering of craters at the Moon's south pole

Credit: ESA /SMART-1 /AMIE camera team; image mosaic: M. Ellouzi/B. Foing

The dark and shadowed regions of the Moon fascinate astronomers and Pink Floyd fans alike.

Our Moon's rotation axis has a tilt of 1.5º, meaning that some parts of its polar regions never see sunlight – the bottoms of certain craters, for example, are always in shadow.

Imaged during summertime in the Moon's southern hemisphere by the Advanced Moon Imaging Experiment (AMIE) on ESA's SMART-1 spacecraft, this mosaic shows a crater-riddled region spanning the lunar south pole.

It is made up of around 40 individual images taken between December 2005 and March 2006, and covers an area of about 500 x 150 km.

The craters visible here include (from right to left, starting with the largest round shape visible in the frame) the Amundsen, Faustini, Shoemaker, Shackleton and de Gerlache craters.

Amundsen is the largest of the bunch at 105 km across, followed by Shoemaker (50 km), Faustini (39 km), de Gerlache (32 km) and Shackleton (19 km).

This group of craters all look different, see varying levels of sunlight and display a range of interesting properties.

Shackleton crater, the small circle visible to the left of centre, contains the south pole within its rim.

By using SMART-1 images to explore the number of small impact craters scattered on the smooth, dark surface surrounding Shackleton, scientists have found this crater to be older than the Apollo 15 landing site (3.3 billion years), but younger than the Apollo 14 site (3.85 billion years).

Shoemaker crater, visible to the upper left of centre, is notable because of the 1999 Lunar Prospector mission, which deliberately crashed into the crater in an attempt to create a detectable plume of water vapour by heating any water ice that may have been present.

No vapour was spotted. However, all is not lost; some permanently shadowed regions have been in the dark for millions of years, and it is still possible that they may contain water ice deposited by comets and water-rich asteroids.

Studying the dark depths of these craters could tell us not just about the history of the Moon, but also about Earth, helping us to understand better how, and how much, water and organic material may have been transferred from the Moon to Earth over its history.

ESA's SMART-1 Advanced Moon Imaging Experiment (AMIE) maps Lunar North Pole

Credit: ESA

This mosaic of the lunar north pole was obtained with images taken by the Advanced Moon Imaging Experiment (AMIE) on board ESA's SMART-1.

The pictures were taken between May 2005 and February 2006, during different phases of the mission.

The mosaic, composed of about 30 images, covers an area of about 800 by 600 km.

The lunar near-side facing Earth is at the bottom of the map, while the far-side is at the top.

A number of interesting lunar craters are indicated.

Peary, visible in the centre of the mosaic, is the crater closest to the lunar north pole.

It is nearly circular (about 73 km across), with an eroded rim and a relatively flat crater floor marked by smaller craters inside.

The southern part of its interior is permanently in shadow, making it difficult to image.

It was named after the American polar explorer Robert Edwin Peary (1856-1920).

Byrd, in the bottom-centre part of the mosaic, is a crater about 94 km across. Its rim is eroded, and its floor was once flooded by lava which left it nearly flat.

It was named after the American polar explorer Richard Evelyn Byrd (1888-1957). Hermite is an impact crater about 104 km across, located along the northern lunar limb, close to the north pole of the Moon.

From Earth, this crater is viewed nearly from the side, illuminated by oblique sunlight. It is eroded and has a rugged outer rim, incised from past impacts. Its interior forms a wide plain marked by numerous tiny craters and low hills.

Sylvester, about 58 km in diameter, is an almost-circular lunar impact crater visible on the left-hand side of the image.

It is located along the northern limb, and has a sharp-edged rim. Due its location, it only receives sunlight at a low angle.

It is named after the English mathematician James Joseph Sylvester (1814-1897).

Plaskett crater, about 109 km across, is located on the northern far-side of the Moon, 200 km from the north pole, near the lunar limb.

It receives sunlight at a low angle.

When obtaining the images, SMART-1 was flying over the north pole at a distance of about 3000 km, allowing large-field (about 300 km across) and medium-resolution views (300 m/pixel).

Each individual image includes areas imaged with colour filters and a more exposed area.

The differences have been corrected accordingly to obtain this mosaic.