SPOT THE DIFFERENCE

This web site, run by ALPO and the BAA, allows amateur astronomers to look for differences between spacecraft images of the Moon taken at different times. The images have to be very similar in appearance in terms of illumination, viewing angle, image contrast and resolution. We will present you with one set of images, to try, each month.

There are lots of small scale changes that occur on the Moon due to meteorite impacts, landslides etc. This 2015 LPSC Conference Abstract, discusses the results of an automated search where ~24 thousand low reflectance changes, ~2 thousand high reflectance changes, and 225 new impact craters were discovered that were not present in earlier images They have also found landslide features on steep slopes, one of which was at least 2 km long, and evidence for an ejecta pattern from a 18m diameter fresh crater lying up to 30km away. However automated image systems can sometimes be tricked by shadows, and humans maybe better at differentiating between real physical, and optical, changes.

As an experiment a pair of images, taken some time apart, will be presented every so often, and users can look for, and circle, any changes they see on a copy of the downloaded images. This challenge, and the way it is presented, will evolve over time, for example we might use image correlation software to find the changes, and then let users rate the detections. But we are not ready for that just yet, so let’s get started with the manual approach, as it’s easy to do right now!

We will trying different temporal image pairs of the lunar surface approximately every month. Click on the top most named lunar feature to find the latest:

Rimae Sosigenes

For 2016 October we are looking at one part of the multiple rille system, Rimae Sosigenes. About 45 km WSW of the crater Sosignes where we find some Meniscus Hollows on the bottom of an old volcanic vent that cuts through a graben.

SW Rim of Aristarchus

For 2015 August we are looking at the SW rim of Aristarchus, a very bright crater not far from the NW limb of the visible face of the Moon.

NNE Rim of Picard

For 2015 July we were looking at the steep ~45° slopes of the NNE rim of Picard crater, located in Mare Crisium.

Apollo 14 Landing Site

For 2015 May we were looking at the Apollo 14 landing site and detecting changes due to sunglint off of shiny heat insulation material that is now strewn across the surface. This project is now closed and was discussed in the June ALPO/BAA Lunar Section Newsletters.