Taking a SMART look at the mountains of the moon

A European Space Agency (ESA) scientist has today presented to the European Planetary Science Congress in Münster some stunning three-dimensional images of mountainous terrain near the lunar south pole. Detlef Koschny‘s pictures were taken with a camera onboard ESA’s Smart-1 lunar orbiter, the flight dynamics of which I did some work on during the mission planning stage, when I worked at ESA’s operations centre in Darmstadt.

Lunar “Peak of Eternal Light” near the moon’s south pole, with the Shackleton Crater just off the right hand side of the image. The small crater in the centre of the image is around 1 km across (source:ESA/SMART-1/Space-X).

Smart-1 was designed primarily as a spacecraft propulsion testbed, but the various instruments bolted onto the probe in order to help justify the mission’s ~€110m cost returned a great deal of useful science data. The price tag, by the way, is around one fifth that of a major ESA science mission, and Smart-1 has proven to be highly cost-effective.

Smart-1 was the first European interplanetary spacecraft to use an ion engine as its propulsion system. Ion engines work by ionising an inert gas with electricity generated by solar panels, and expelling the gas in a continuous stream out the back of the spacecraft. This produces a forward thrust which provides a small but steady acceleration with minimal energy costs.

The spacecraft’s trajectory to the moon was a long one, and began with an expanding orbit of the earth, up to the point where the moon’s gravity takes over. The spacecraft then moved in a slowly contracting lunar orbit, with a minimum altitude of 300 kilometres. No-one involved with Smart-1 was in a hurry to get to the moon, which is a three-day journey as the astro-crow flies. We were more interested in proving the propulsion technology and learning lessons for future missions.

At the end of the science mission, controllers crashed the craft onto the moon’s surface in an act of spectacular cosmic vandalism.

The AMIE camera used to capture the images was a single-lens device, and producing 3-D reconstructions of the lunar surface involved using the brightness of light reflected from the surface to determine the slope of the terrain. Then, by comparing a number of images, the researchers were able to construct a digital elevation model which produces shadow patterns that match those observed with the camera.

The mountain peak of interest here is the so-called “Peak of Eternal Light” located near the rim of the Shackleton Crater by the lunar south pole. Peaks of eternal light are defined as points within the solar system eternally bathed in sunlight. There are several such peaks on the moon, and they are of interest as sites for future lunar colonies.

AMIE took over 100 images of the polar peak, and these show shadowed craters which may hold water ice deposited over millennia through cometary impacts, and hydrogen and oxygen particles in the solar wind. With constant sunlight for power generation, stable temperatures and the presence of water, the lunar south pole could be a cosy location for humanity’s first off-world colony.

You can view the high-resolution images on the Europlanet website.