The Moon is seriously old and our objective here at Moon Zoo is to study its surface with the time and detail that cannot be afforded by a small team of scientists. Earth’s closest neighbour and only natural satellite represents the largest and brightest object in the sky second to the Sun, and plays a crucial physical role to life here on Earth. But as the only other body to have been walked upon by man, what do we actually know about the Moon? Why is it so important to continue to study? And what can Moon Zoo’s 47,000 participants do to help?
One of the main focusses at Moon Zoo is to examine the distribution of craters in various regions in terms of their size and frequency. By determining this relationship, we can then independently estimate surface ages of different areas that have been examined by the community. Discerning these surface ages is key to understanding the history of the early Solar System, as the Moon is thought to have formed just 30-50 million years after its birth 4.5 billion years ago. The colossal impact of the Mars-sized body, Theia, into the early Earth stripped the outermost layer of our planet and returned it to a molten state, whilst the ejecta was captured in orbit and accreted to form the Moon. Although not perfect, this hypothesis explains the relatively small size of the Moon’s core and overall lower density, since it coalesced mostly from lighter crustal material. Whilst the Moon’s internal structure is differentiated into a core, mantle and crust in a similar way to the Earth’s, its rapid cooling saw tectonic and volcanic activity cease around 3.5 billion years ago. The combination of the Moon’s inactive geology and highly tenuous atmosphere has enabled its surface to become one of the most ancient, and well-preserved in the Solar System. From this almost perfectly kept record, we are not only able to look into the Moon’s past, but also unravel some of the mysteries surrounding the Earth’s history, the early Sun, and previous Solar System environments.
On Earth, tectonic, volcanic, and weathering activity has destroyed much of its early record, which is why we look to the Moon to understand our own history. We use observations of different surface features and lunar samples to date particular regions, which can help indicate events that occurred in the inner Solar System. This can, for example, be used to date periods of heavy bombardment from asteroids, which enables us to investigate the frequency of such events in Earth’s history. The samples obtained from the Moon originate from its outermost layer, known as the regolith, which is comprised of fine dust formed by impact processes. The Moon’s practically vacuous atmosphere does little to interfere with this layer, so it is able to preserve the impact fragments and provide insight into the composition and origin of colliding bodies. The regolith also incorporates particles from the solar wind, which allows us to examine how the Sun has changed over its lifetime.
Moon Zoo is helping to uncover the lunar geological evolution by analysing high-resolution images from NASA’s Lunar Reconnaissance Orbiter (LRO), in order to expand our knowledge of past impact, tectonic and volcanic activity on the Moon. Alongside crater counting, the other current primary focus is the identification of boulders, which can indicate depth of unconsolidated material. Another outcome of this search will be the production of boulder-density maps, which can be used for future lunar missions to indicate safe (or very hazardous!) landing sites.
To date, the Moon Zoo community has already made over 3.5 million visual classifications with images from LRO, alongside many unusual geological features; the project has also been very successful in identifying spacecraft debris, rover tracks and even astronaut footprints! Data already gathered from the work of Moon Zoo participants on the Apollo 17 landing site are well on their way to producing the first comprehensive paper showing these results, which is scheduled for submission shortly. The current Apollo 12 landing site has also received a great deal of interest and will soon be drawing to a close for full analyses by the Moon Zoo science team. The next step will be analysing an entirely new data set, which will most likely delve into the rare maria on the more mysterious dark side of the Moon.
There is still a great deal more to understand about our planet’s closest relative and the clues it holds to the history of the bodies around it. Until the next stage of the project is launched, we implore you to keep clicking and help demonstrate the strong impact of citizen science on lunar research!
Every now and then Moon Zoo produces an image that just needs to be shared. Forum regular kodemunkey found another fresh white crater a while ago. I say another one because the forum contains many examples of these eye-catching recent impacts. And when I say recent I mean these impacts are millions rather than billions of years old. So it’s easy to be a little blasé when yet another one is posted. Until one comes along which hits you between the eyes. We featured one last year. And now we have another – a small unnamed crater on the western edge of Mare Vaporum. Click on the image for a bigger, better view.
Here it is in context – one small crater amongst many. The Lunar Reconnaissance Orbiter picked it out and highlighted its symmetrical beauty.
The impact produced some lovely feathery ejecta patterns (which are worth exploring even closer on the NAC images) and a gloriously bumpy and bouldery crater floor. Follow the links above (and this additional resource) for more information on fresh craters or just click on the first image, click again to zoom and sit back and enjoy.
Linné crater is a young, well preserved impact crater on the western edge of Mare Serenitatis, at coordinates: latitude = 27.7, longitude = 11.8. It is 2.2 km in diameter and bowl-shaped and is often cited as a good example of a fresh impact crater. Its actual age is unknown but thought to be less than 10 million years.
It has been used to investigate how cratering occurs in mare basalts and the report from the 42nd Lunar and Planetary Science Conference (2011) has a very good description of the crater and compares it to the terrestrial Barringer Crater (aka Meteor Crater). The report can be found here: Linne: Simple Lunar Mare Crater Geometry from LRO Observations
There is some controversy about Linné crater to do with ‘transient lunar phenomena’ (TLP) maybe caused by outgassing. In the nineteenth century some astronomers believed that they had seen changes around the crater, in some cases they said that the crater had vanished leaving only a mound behind. This is discussed here: The Linné Crater Controversy
[NASA/GSFC/Arizona State University]
Colour coded shaded relief map of Linné crater created from an LROC NAC stereo topographic model. The colours represent elevations; cool colours are lowest and hot colours highest.
The following site contains a movie of a “fly around” Linné crater:
We are used to seeing different kinds of craters on the Moon Zoo forum. In particular we collect dark haloed craters and fresh white craters. Impacts can excavate rocks and material beneath the lunar regolith and this “fresher” material forming the ejecta blanket sometimes looks a very different colour to the rest of the surrounding area due to its higher or lower albedo.
Forum member kodemunkey recently found a couple of impacts which at first glance were hard to classify – you could say they were impacts of two halves. Are they fresh whites or dark haloed? Or is it just a trick of light and shadow? I think that’s exactly what we are seeing in the first crater. The combination of a high Sun, uneven terrain and a deep impact has produced an image of a crater half in shadow. The second crater is slightly more difficult to call. Both make striking images. Why not have a closer look and see what you think.