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Poster by:I. AntonenkoPlanetary Institute of Toronto, Toronto, Canada& University of Western Ontario, London, CanadaPlanetaryInstituteofToronto@yahoo.ca

MoonMappers Team Programming Team: Cory Lehan, Joe Moore, Sean McKenna, Dan StoughtonEducation Team: Georgia Bracey, Kathy Costello, Ellen ReilleyModeration / Social Media: Katharina “Kamasterdo”, Joe Rhea

2011 - 2013 CosmoQuestCreative Commons Attribution-NonCommercial-ShareAlike 3.0Funding for this project is provided under NASA grant #NNX 09AD34G, from the NASA Lunar Reconniassance Orbiter, and from the Maryland Space Grant Consortium via the NASA Lunar Science Insitute.

Moon Mappers

Effects of Incidence Angle on Crater Detection and theLunar Isochron System: Preliminary Results from theCosmoQuest Moon Mappers Citizen Science Project.

S.J. RobbinsSouthwest Research Institute, Boulder, CO & University of Colorado at Boulder, Boulder, COstuart.robbins@colorado.edu

P.L. GaySouthern Illinois University Edwardsville, Edwardsville, IL pgay@siue.edu

C. LehanSouthern Illinois University Edwardsville, Edwardsville, ILcorylehan@gmail.com

J. MooreSouthern Illinois University Edwardsville, Edwardsville, ILjmoore@siue.edu

CosmoQuest is a production the Center for STEM at SIUE & Astrosphere New Media,in association withUniverse Today, Bad Astronomy, & numerous partner organizations.

To find out how your organizatio can get involved, email getinvolved@cosmoquest.org

@MoonMappers is a @CosmoQuest citizen scienceproject. Come be part of Lunar exploration & #Hangout on #CQX. Images are now standing by. about 1 day ago

References[1] Robbins S.J. et al. (2012), LPSC 43, #2856. [2] Robbins S.J. et al., in review (GRSL). [3] Robbins S.J. (2013), LPSC 44, #1619. [4] Hartmann W.K. et al. (1981), in Basalt Volcanism on the Terrestrial Planets, Pergamon Press, NY, 1049-1128. [5] Neukum G. & Ivanov B.A. (1994), in Hazards due to Comets and Asteroids, UofArizona Press, Tuxton 359-416. [6] Wilhelms D.E. (1987), The Geologic History of the Moon. USGS Prof. Pap. 1348, pp302. [7] Ostrach L.R. et al. (2011), Planet. Crater Cons. 2, #1107.

Comparing Volunteer and Expert Individual Crater Markings: Volunteer results are calibrated by periodic comparisons with expert markings. The individual Moon Mappers users' markings (blue), and their combined results based on the cluster code algorithm (green), generally have very good agreement with the expert markings (red).

IntroductionThe Lunar Reconnaissance Orbiter's Narrow-Angle Camera (LROC NAC) provides the first opportunity to study the same craters at a variety of solar lighting conditions. In this work, cra-ters in the Apollo 15 landing region were analyzed to explore the effects of solar incidence angle on crater detection. The extensive crater cataloging task was crowd-sourced through CosmoQuest's Moon Mappers project [1].

Effects of Solar Incidence Angle on Crater DetectionThe same region of the Apollo 15 landing site is examined by Moon Mapper volunteers at a wide range of incidence angles spanning 27.5° to 83° relative to normal (noon). When the sun is lower on the horizon (e.g., sun angle ~80°), our our volunteers identify more craters.

• Craters population behaves as would be expected.• Larger craters appear to represent a population in production (roughly following established production functions

[4,5]). • Smaller craters are in empirical saturation, where every new crater that forms removes an equivalent num-

ber/fraction of other craters (their cumulative frequency distribution slope is shallower).When the sun is high overhead (e.g., sun angle of ~30° in our study), our volunteers find that craters are much more

difficult to identify. • Crater populations measured at high sun contain ~4x less craters than the population observed at ~77°. • This is expected, since high sun angles emphasize albedo over topography [e.g. 6] making topographic features

more difficult to identify. Overall, these data suggest that the "ideal" sun angle range for crater identification is constrained within 58° < i < 77°, similar to recent work [7].

Effects of Solar Angle: Seven NAC images, which cover the same area of the Apollo 15 landing site but have different solar incidence angles, have been fully examined by Moon Mappers users to-date. The resulting data is shown here as cumulative size-frequency distributions. 2.0 Ga iso-chrons are plotted over the data, showing general agreement with isochron slope until empirical saturation is reached. Crater populations measured with the sun high overhead (sun angle of ~30°) tend to have ~4x less craters than those measured when the sun is close to the horizon (sun angle of ~77°). The data suggest an "ideal" sun angle for crater counting of 58° < i < 77°.Conclusions

Moon Mappers volunteers have made over 1.2 million crater identifications and measurements in less than one year. This number translates into a catalog of 10s of thousands of final craters. The Moon Mappers data has been found to be consistent with expert results and useful for crater age modeling. These data also show that solar in-cidence angle seriously affects crater detection and measurement. The optimal angle for crater counting was found to be 58° < i < 77°. As we further develop this tool, we will be able to gather the data needed to answer questions that could not be done before, with future work looking at crater saturation and seismic shaking.

Comparing Volunteer and Expert Crater Population Statistics: The crater population of a ~±0.13° (17.1 km2) region around the Apollo 15 Falcon lander was evaluated by Robbins [3]. Cumulative size-frequency distributions of the Moon Mappers users' data is in good agreement with Robbins' [3] results from three different sets of image data.

Data Source: Moon Mappers ProjectVolunteers from around the world have been examining 450 x 450 pixel sub-images, identifying and annotating craters and other features. To-date, these citizen scientists have found and measured 1.2 million craters. Compiling the Crater CatalogEach 450 x 450 pixel sub-image must be annotated by 15 different people to be considered complete. After all sub-images from a given NAC are completed, a 3-D clustering code is run [2] to identify unique craters. Craters that have been identi-fied by >60% of the volunteers who looked at the sub-image containing that crater (N>9 markings per cluster) are saved to a final crater catalog.

CalibrationAt random intervals, volunteers are shown a cali-bration image that (unknown to them) has already been marked by an expert. After annotating this image, the volunteers are shown a comparison of the expert's and their results in order to promote quality work. The scores from these calibration images are used to assign confidence levels to each volunteer's results during data reduction (clustering).

Validity of Moon Mappers DataThe volunteers' results are compared to those of experts by considering:

• Crater markings on individual craters• Crater population statistics for entire regions.

These show that Moon Mappers data is in good agreement with experts and can be used for model-ing crater ages of terrains as old as ~3.5 Ga.

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