Discover the Smithsonian Moon Exhibit On-Line

This February the Smithsonian National Air and Space Museum in Washington D.C. opened an exhibit titled “A New Moon Rises: New Views from the Lunar Reconnaissance Orbiter Camera.” The exhibit, which showcases some of the most spectacular images acquired by the Lunar Reconnaissance Orbiter Camera (LROC) since 2009, is scheduled to run until December 2016. If you live in Washington D.C., or are planning a trip there in the near future, I would encourage you to check out the exhibit, especially since admission to the museum is free.

For the rest of us, the Smithsonian has kindly provided an on-line version for us to experience. Like the physical exhibit, the virtual “A New Moon Rises” exhibit is divided into six themes (Global Views, Exploration Sites, Discoveries, Vistas, Topography and Craters), which can be accessed through the menu bar at the top of the page.

Within the virtual exhibit, you will find some truly spectacular images. Some of my favourites are highlighted below.

Where the Sun Never Shines

Unlike the Earth, the Moon’s axis is not tilted very much. This means that sunlight hits the lunar poles at a very low angle (like at sunrise or sunset on Earth) pretty much all of the time. Some high areas, like mountains and crater rims, will get at least some sunlight most of the year, while low areas, like crater depressions, will get effectively no sunlight, ever. This image of the south pole was created by combining thousands of images taken over a lunar year. It shows what percentage of the year each area is hit by sunlight. The shading is scaled so that areas that get sunlight 100 % of the time show up as white, while those that never get sun are black.  The black areas, known as permanently shadowed regions, get very cold and so are believed to be places where water ice is trapped and preserved from evaporation by the hot sun.

Image Credit: NASA/Goddard Space Flight Center/Arizona State University 

Oh Orientale!

Pairs of stereo images from the LROC Wide Angle Camera, along with altimetry data from the Lunar Orbiter Laser Altimeter, allow topography to be determined for the entire lunar globe.  This image shows the topography of the western limb of the Moon, centred on the Orientale basin.  Orientale is the youngest of the large lunar impact basins and has not been flooded by much lava. As a result, its topography is readily revealed, showing multiple impact basin rings. Here, reds and browns denote high elevation, greens and blues represent medium elevation, and deep blues and purples show areas of very low elevation. 

Image Credit: NASA/Goddard Space Flight Center/Arizona State University 

Giordano Bruno in 3D

Giordano Bruno is one of my favourite craters (of course, I covered it in one of my earliest Planetary Geolog posts). This image shows the crater from an oblique angle, which highlights the topography of the rim and floor features of the crater. The sunlight also shows off the interesting landslides on the crater walls.

Image Credit: NASA/Goddard Space Flight Center/Arizona State University 

I hope these few examples will inspire you to explore the virtual “A New Moon Rises” exhibit yourself and find your own favourites.


Source: 
A New Moon Rises: New Views from the Lunar Reconnaissance Orbiter Camera. Smithsonian National Air and Space Museum On-line Exhibits, Accessed May 31, 2016.

Many Small Nuggets from the 47th Lunar and Planetary Science Conference

Tuesday Night Poster Session at the LPSC 2016.
I might be in there somewhere...
Image credit:  Lunar and Planetary Institute. 

This year's Lunar and Planetary Science Conference (LPSC) was another success. I again went as an independent researcher, but this time I was also looking for employment opportunities. I got a few leads, which I will follow up in the next few weeks.

I also rejoined the official LPSC microblogging crew. Some of you may have followed my short posts on Google+ during the conference. As usual, I am reproducing my entire complement of LPSC microblogs, plus appropriate links (if available), here on the Planetary Geo Log. Again, the intent is for you to digest a few small nuggets at a time. I hope to write up some of these in future blogs, so keep an eye out. If you would like to learn more about any of the posted topics, please feel free to make a request in the comments.

Sunday March 20, 2016
1)  Hello folks. I am at the Lunar and Planetary Science Conference again this year and will be microblogging on Google+. I hope you enjoy my observations of the conference.  
(http://www.hou.usra.edu/meetings/lpsc2016/)  

2)  Attended this year's #Microsymposium57 before #LPSC2016. I'll be posting some highlights......
(http://www.planetary.brown.edu/html_pages/micro57.htm)  

3)  David Paige has found that there are more volatiles in low latitude craters at the lunar poles, because those craters catch the poleward-migrating volatiles before they can reach the high latitudes of the poles. #Microsymposium57 before #LPSC2016.    

4)  Barb Cohen is looking for "operationally useful amounts of water" on the Moon, which means large quantities. She proposes this can be done using cube satellites. #Microsymposium57 before #LPSC2016.    

5)  Mahesh Anand tells us that ESA considers the Moon to be the primary target for human exploration after the ISS. #Microsymposium57 before # LPSC2016.    

6)  Tony Colaprete and Jen Heldmann told us about the proposed Resource Prospector mission. It consists of a rover that will take measurements and samples at several locations on the lunar pole. #Microsymposium57 before #LPSC.    

Monday March 21, 2016
1)  Catherine Johnson shows that the magnetic field on Mercury is strongest in the Caloris basin and the magnetic field is at least as old as the Caloris basin.   
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1391.pdf)

2)  L. Hood noted that you need a long-standing magnetic field to explain the magnetic signatures seen at Caloris and Sobkou basins on Mercury. So, Mercury would have had a magnetic dynamo at the time these basins formed.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1301.pdf)

3)  The models of P. James suggest that the lithosphere of Mercurry is 32 (+/-15) km thick.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1992.pdf)

4)  C. Fasset shows that crater degradation on Mercury happens much faster than on the Moon.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1046.pdf)

5)  Robbie Herrick noted that Mercury has more craters <10 km in diameter than would be expected for the number of craters >10 km in diameter. This would be due to a larger number of secondaries. If so, the oldest surfaces on Mercury could be 100 m.y. younger than previously estimated.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2766.pdf)

6)  Congratulations to last year's Dwornik student award winners:
      Robert Jacobson - U Tennessee,
      Hanna Susorney - John Hopkins,
      Johnathan Oulton - Florida State,
      Hank Cole - Colorado School of Mines.   

7)  Alan Stern reported on the New Horizons mission results so far. Although the flyby of Pluto is complete, only half of the data has been transmitted, because lower transmission rates were selected to keep costs down. The other half of the data is still to come. What additional exciting things will we learn about Pluto?    
(PDF Presentation of Alan Stern's Talk)
(Video of Alan Stern's Talk)

8)  Pluto has 4 small satellites in addition to Charon. The outer-most, Hydra, rotates 100 times about its axis for each orbit around Pluto. It's quite mesmorizing in this animation that Alan Stern showed.
(Animation of Pluto's Satellite's Orbits)
Comment on Google+: Wow. Any particular reason for that? (spin:orbit resonances?)
My reply: No, they're not quite sure. Just sat in on a talk by S. Porter, where they discussed the small satellites. All have retrograde rotations, which is odd, so they suspect this may be related to some kind of tidal state.

9)  Pluto's large, bright, smooth plane, called Sputnik Planum, is thought to be an ancient impact basin that is filled with nitrogen ice. This ice shows evidence of glacial flows at the northern edges according to Alan Stern.    

10)  Using GRAIL Gravity data from the Moon, Maria Zuber showed that cryptomaria (hidden mare deposits) in the Schiller-Zucchius basin do NOT extend to a depth of 10 km. This is not a surprising result, but it's good to have a confirmation of this.   
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2105.pdf)

11)  Tony Colaprete reported on LADEE data for the thin lunar atmosphere, or exosphere. Titanium and magnesium concentrations in the exosphere are somewhat correlated with mafic deposits on the surface and aluminum deposits are somewhat corelated with surface highlands, though the surface compositions cannot completely explain the exosphere compositions.
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2635.pdf)

12)  The Pluto/New Horizons research articles in Science are all open access!! Enjoy...    
(http://science.sciencemag.org/content/351/6279)

13)  S. Porter tells us that the moons of Pluto are in extremely stable orbits and their surfaces (as far as we can tell with the limited available data) are cratered and old. So, these moons are not new or ephemeral objects, but have been orbiting around Pluto for a long time.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2390.pdf)

14)  NASA Night at #LPSC2016. NASA is looking for community input on how we use NASA data. Foreign input is also welcome. There will be a link posted on the LPSC webpage with instructions on how to submit your input. I will update this microblog post with the link as soon as it goes up.
Instructions for submitting input can be found at: (http://science.nasa.gov/researchers/sara/grant-solicitations/nasa-request-information-assessing-planetary-science-communitys-use-planetary-science-division-facilities/)

15)  NASA Night at #LPSC2016. Cosmoquest was mentioned as one of the organizations that won an Education and Public Outreach grant this year. Congratulations #Cosmoquest!
(https://cosmoquest.org/)

16)  NASA Night at #LPSC2016. Jim Green tells us that the NASA planetary science budget got $270 million more than was requested this year!!
Total budget is $1.63 billion.    

17)  NASA Night at #LPSC2016. This was Jim Green's closing slide for questions.

18)  Really enjoyed meeting old friends and new at the Students Reception.    

Tuesday March 22, 2016
1)  Jeff Plescia told us that impact melt flows on the Moon show evidence of multiple pulses of material from the same impact.   
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2585.pdf)

2)  Jason Cook talked about the distribution of non-volatiles on Pluto. Apparently this means water, which I think of as a volatile. But water does not act like a volatile on Pluto, because of the extremely cold temperatures. Jason finds that water is widely destributed on Pluto, predominantly as fine particles.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2296.pdf)

3)  Misha Kreslavsky found large-scale dendritic patterns, with a topographic range of 20 meters, in parts of the lunar maria.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1331.pdf)

4)  Lisa Gaddis showed that M3 data can be used to identify volcanic pyroclastic deposits on the Moon.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2065.pdf)

5)  Tom Giguere suggests that the floor of Gassendi crater, a floor-fractured crater on the north-west shore of Mare Humorum on the Moon, shows evidence of drained lava lakes.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1884.pdf)

6)  Carl Allen used Diviner data, collected during a lunar eclipse, to show that pyroclastic deposits in the Aristarchus region of the Moon cool faster than other materials in sinuous rills, maria, or mare rays. The thermal inertia of pyroclastic material must, therefore, be lower, possibly due to a much finer grain size.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1309.pdf)

7)  Carolyn van der Bogert showed that the Dark Mantle Deposits of Taurus Littrow are actually older than the surrounding maria, even though they look younger. This is because small craters in the dark mantle deposit are in saturation and have experienced preferential degredation, while the small craters in the nearby maria are still in production, resulting in more craters at that size.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1616.pdf)

8)  Tuesday poster sessions were such a whirlwind, I didn't get a chance to microblog about anything.

9)  30th annual Hawaii Party was it's usual fun. Really enjoyed chatting with Tom Giguere and Steve Ruff.   

Wednesday March 23, 2016
1)  Daniel Moriarty and Makiko Ohtake presented back-to-back competing interpretations for the interior of the South Pole-Aitken basin on the Moon. I confess, I am confused....    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1735.pdf)
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1414.pdf)

2)  Noah Petro presented work that supports the presence of cryptomare deposits in the Bhabha region of South Pole-Aitken basin on the Moon. During the question period, Apollo 17 astronaut Jack Schmidtt noted that one of the flat-floored irregular craters in the region may not be a flooded impact crater, but rather a volcanic caldera related to the cryptomare volcanism period.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2669.pdf)

3)  Paul Spudis identified a number of units around the edges of Mare Crisium on the Moon. These units poke through, and so pre-date, the mare material of the basin. Paul suggests that these may be remnants of the Crisium impact melt sheet and so would make good targets for future sample-return missions.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1463.pdf)

4)  Based on low-angle impact experiments, Pete Schultz proposes that so-called "double impacts", which have been identified in GRAIL gravity data from the Moon, may actually be due to a single low-angle impact. What happens is the approaching bolide hits the surface at an oblique angle, causing the top of the bolide to decapitate and hit the surface in a second location down-range, producing what looks like a double impact.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2931.pdf)

5)  Shared from Stuart Robbins.
Lisa Gaddis: NASA’s Cartography & Imaging Sciences Node contains >850TB of data, growing at ~120TB/yr.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2281.pdf)

6)  Just uploaded the electronic version of my #LPSC2016 poster. You can see it here...    
(http://www.hou.usra.edu/meetings/lpsc2016/eposter/2948.pdf)

7)  Pamela Gay told us about the exciting funding developments happening for the #Cosmoquest project during our Cosmoquest community meeting at #LPSC2016.    

8)  At the #Cosmoquest community meeting (during #LPSC2016), Andrea Jones encouraged us to spread the word about International Observe the Moon Night, happening this year on Oct. 8, 2016. Now is the time to start planning your event. Don't forget to register your local event, whether it's a big museum function or a small neighbourhood get together, so InOMN can highlight how global this celebration truly is! Instructions on how to get involved can be found under the Get Involved tab on the web link below.    
(http://observethemoonnight.org/)

Frustum
Image credit:  Wikipedia. 

9)  New Vocabulary Word from R. Beyer's talk at #LPSC2016. Frustum: A diagram illustrating the angle a camera is pointing towards the target surface.    

10)  Planetary Spatial Infrastructure session at #LPSC2016 was very interesting. Best quote has got to be "Cartography is important to cartography." This means that Cartography, as the manipulation of digital data so that it can be presented in a map, is important to Cartography, the process of creating maps.     
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/sess453.pdf)

11)  LEAG Networking Session at #LPSC2016. A group of young scientists are gathered around Apollo astronaut Jack Schmidtt, soaking up his wisdom.    

12)  Smart people tend to be more prone to unintentional bias. They tend to feel they are immune to this bias, because they are smart. So recognize that you have biases, know what they are, and work to overcome them. #WomenInPlanetaryScience and #LPSC2016.    

13)  Being self-aware of your own biases and working on those is not enough. The culture and institutions in the community need to be changed too, to help overcome this bias problem. Senior and mid-career members, who are less vulnerable, need to take the initiative in this regard. #WomenInPlanetaryScience evening at #LPSC2016.    

14)  Discussion section of the #WomenInPlanetaryScience evening at #LPSC2016. was great.    

Thursday March 24, 2016
1)  Systems engineering is ensuring that you don't design misunderstandings into your system. #NextGenWorkshop Scientists and Engineers: Learning to Work Together at #LPSC2016.    
(Video about system engineering, recommended by the presenter, Lee Graham )

2)  Think of mission requirements as dollars in a different form. You want the minimum necessary requirements to cover the scope and objectives of your entire mission, no more and no less. #NextGenWorkshop Scientists an Engineers: Learning to Work Together at #LPSC2016.    

3)  Totally amazed by the interesting people who stopped by my unconventional planetary poster about using financial modeling techniques for identifying basalt spectra.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2948.pdf)
(http://www.hou.usra.edu/meetings/lpsc2016/eposter/2948.pdf)

4)  The annual Arizona Party was fun, but I was too beat from my poster session to take advantage of the dance floor and DJ. Does anyone know if there was much dancing this year?    

Friday March 25, 2016
1)  Michael Nayak found that magnetic data from the South Pole-Aitken basin suggests the existence of several new magnetic paleo-poles on the Moon, which had not been previously identified.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2506.pdf)

2)  Lon Hood suggested that the absence of magnetization on the rims of large lunar impact basins may be due to their being erased by subsequent volcanic flooding. However, Mark Wieczorek pointed out that his earlier work shows that mare layers cool too quickly for their heat to be able to erase the magnetic signature.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1303.pdf)

3)  Rona Oran used simulations to model the behaviour of the lunar magnetic field during large-scale impact events. Her work shows that the magnetic field is increased all over the Moon during an impact event, not just at the antipode. However this increase is too small to explain observed magnetizations, thus supporting a stable core dynamo as their source.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/3057.pdf)

4)  Mark Wieczorek gave a fascinating talk about the depth of lunar magnetization. Almost the entire Moon is magnetized and most of it has a deep origin. This means that impact magnetization, which only affects the surface, is not the dominant magnetizing process on the Moon. Similarly, volcanic intrusions cannot be used to explain magnetism on the far side, where volcanism is very limited. Therefore, most of the magnetization seen on the Moon must have been accumulated during slow cooling of the primordial crust in the presence of a stable dynamo. Magnetization of the farside crust would have been locked in by 230 million years after the formation of the Moon, so the dynamo must have been in place by then. This is even earlier than the oldest magnetized samples we have from the Moon, which have been dated at 4.25 billion years old (~250 million years after the formation of the Moon).    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/2288.pdf)

5)  D.A. Patthoff mapped two populations of ridges on Enceladus, one old and one recent. Based on these, the following tectonic history was proposed: compression of the crust associated with its formation, followed by a long tectonically quiet period, culminating in a recent period (<100 m.y.) of compression possibly associated with thickening of the crust due to cooling of the underlying ocean. What is not known is what are the implications of this history or the evolution of life and how long before the ocean completely freezes over.
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1772.pdf)

6)  Mike Bland proposes that the grooved terrain of Ganymede is formed when magmatic intrusions heat the overlying crust. This allows convection in the intrusion to push the overlying crust and bunch it up (like a table cloth) to form sets of parallel grooves.    
(http://www.hou.usra.edu/meetings/lpsc2016/pdf/1287.pdf)

7)  Audience request for some Game of Thrones names on Charon.   

8)  We have reached the end of #LPSC2016. Thank you so much for letting me bombard you with my observations. I hope you enjoyed it, I know I did. Until next year....    

Many Small Nuggets from the 46th Lunar and Planetary Science Conference

Science talk at LPSC 2015.
I was in the room, but I don't think I'm in this picture.
Image credit:  Lunar and Planetary Institute. 

This year's Lunar and Planetary Science Conference (LPSC) was fabulous. I went as an independent researcher and was pleased to see that this is no longer frowned upon like it used to be in the past. Times are tough and budgets are tight. Many scientist are looking at alternate funding models to pay for their research. So, it was wonderful to get a chance to compare notes on this front.

I also was an independent microblogger this year. For the past three years, LPSC organizers have recruited conference attendees to write short blurbs about the session talks on social media. I didn't join the official microblogging crew, but continued to post to Google+ on my own terms - I wanted to reduce the pressure I put on myself.

And just like last time, I am reproducing my entire complement of LPSC microblogs here on the Planetary Geo Log. Don't feel the need to read it all at once, but rather savour a few small nuggets at a time. I hope to write up some of these in future blogs, so keep an eye out.

Sunday March 15, 2015
1)  I am at the Lunar and Planetary Science Conference again this year and will be microblogging about it. I hope you enjoy.....
(http://www.hou.usra.edu/meetings/lpsc2015/)  

2)  The talks at Sunday's session of Microsymposium 56 were really good! Some highlights below:
     - Ejecta from the Moon-forming impact may have reached the asteroids at very high velocities, producing melts that retain a signature of the event.
     - The Procellarum basin may be a palimpsest, formed in a warm crust and mantle.
     - A Procellarum-forming impact would have melted the underlying mantle to the core and distorted the crust at the antipode, allowing later melts to migrate to the surface.
     - The South Pole-Aitken basin may have precipitated mantle melting and also distorted the the crust at the antipode, allowing melts to come to the surface in the Procellarum region.
     - Early lunar impacts may have formed before the overturn of the olivine cumulate layer in the mantle, explaining why we see so little evidence of olivine on the surface. Alternatively, the composition of the mantle may be heterogeneous.
     - Modelling of crustal relaxation for the lunar basins suggests they must have formed when the crust was warm, which is too early in the Moon's history to be consistent with a late heavy bombardment.
     - Modelling of Orientale and seismic studies of the Chixulub crater show that outer rings of multi-ring basins are associated with multiple faults (some listric) that extend all the way to the Moho.
(http://planetary.brown.edu/html_pages/micro56.htm)

3)  The LRO Data Users Workshop took place on Sunday before the LPSC. Some very useful information on how to access and work with the LRO data was presented. Slides from the individual talks can be downloaded from the workshop website.
(http://lunar.gsfc.nasa.gov/datausersworkshop.html)

4) An impromptu demonstration of the Lunar Mapping and Modelling Portal (pub.lmmp.nasa.gov/LMMPUI/LMMP_CLIENT/LMMP.html) was presented at the end of the LRO Data Users Workshop. This tool lets you view a variety of lunar data layers, all registered together.
     I suggested that the ability to do math between the layers would be a very useful addition to the tools and the presenters seemed very receptive to this idea. Maybe that functionality will be added in the future.

Monday March 16, 2015
1)  The Next Generation Lunar Scientists and Engineers panel on tips and strategies for writing successful scientific papers was very informative. The best tips (in my humble opinion) included:
     - Start with your tables and figures and write around them - use them as your outline.
     - If you are having writer's block, start writing your figure captions.
     - Writing is a two step process: dump your thoughts, then word-smith. If you are word-smithing before you have finished dumping your thoughts, you can loose your train of thought or polish something that doesn't really fit anyway, and so end up wasting lots of time.
     - Make sure your paper has only one major take-away message, since that is all that most people will take way.
     - Have your paper end by outlining the next steps; this can be helpful when applying for grants.
     - Reviewers' comments aren't absolute; you can rebut them, preferably with evidence, when you write your response.
     - Rejections often have more to do with timing - the editor doesn't think you can address the reviewers' comments fast enough for their schedule. Unless the editor encourages you to submit this paper to other  journals, consider this an opportunity to edit and resubmit to the same journal.

2)  Overheard at the Students' Reception on Monday:
"I play the stock market, because I want to be a scientist, but I also want to live in a nice house."
... We need to pay our scientists more.      

Tuesday March 17, 2015
1)  Dr. Stuart Robbins gave a fabulous talk explaining the issues with current crater chronology techniques (i.e. figuring out the age of a surface by counting craters). His talk included some amazing animations of plots (of all things) that really helped me to understand some aspects of crater dating that I hadn't before. He's shared these animations with me and I will be posting them on my blog in the near future. Stay tuned.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/2629.pdf) 

 
2)  Using simulations, Dr. Carolyn van der Bogert showed that the crater count-determined model age of a surface depends on the size of your count area. For areas that are less than 100 square kilometers in size, the model age can be incorrect, with smaller areas giving younger ages. Caution should be used when determining the age of very small areas, and multiple regions of the same unit should be aggregated to provide counts over a larger area.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/1742.pdf)

Wednesday March 18, 2015
1) LEAG Town Hall Summary  
     - Planning for a "New Views of the Moon II" is underway. Be ready to contribute to this upcoming volume (whose name is still to be determined). Contributions can also form the basis for white papers in the next decadal survey.
     - Contact your congressman about keeping LRO alive. The Planetary Society  is drafting a letter. Use this as a template for your correspondence, but personalize you letter, because studies show a personalized letter has much more impact than a form letter.
     - The next SSERVI Exploration Science Forum is this July 21-23. There will be talks streamed on the web. (http://nesf2015.arc.nasa.gov/)

2) Dr. Paul Lucey is talking about small lunar craters in the South Pole-Aitken basin. Except he keeps talking about craters in the SPA, pronouncing it "spaa" instead of "es-pee-ay", and all I can think about is getting a massage.
      Okay, I need to add that he found that small craters in SPA were almost exclusively noritic in compositions, which has implications for the composition of the mantle under SPA.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/1655.pdf)

3) Dr. S. Lawrence pointed out that GRAIL lunar gravity data does not support the presence of a basin in the Australe region of the Moon.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/2739.pdf)
 
4) Just finished giving my talk on the complexity of cryptomaria in the Mare Humorum area of the Moon. Whew! Now I can get back to microblogging.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/2808.pdf)


Thursday March 19, 2015

1) Dr. Aileen Yingst used the MAHLI camera on the Mars Curiosity rover to show that fine grained deposits in Gale crater were formed by settling from suspension. The suspension medium is most likely water, because there are no aeolian features present.
     Dr. Yingst and I talk about this some more later and further concluded that the larger grains that can be seen interspersed among the fine grains could not have been carried by wind processes, again supporting the hypothesis that these materials were deposition by settling in water.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/1378.pdf)

2) Dr. Rebecca Ghent looked at radar data of the lunar regolith and found that rocks on the surface break down and disappear within about 1 billion years. Rocks within the regolith, on the other hand, persist for long periods of time, well beyond their brethren on the surface.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/1979.pdf)  

3) A big thank you to Scott at the JMARS booth, who took time during Thursday's poster session to try and solve my JMARS issues.
(http://jmars.asu.edu/)


Friday March 20, 2015
1) Dr. H. Nekvasil conducted experiments that show how crystallization of plagioclase under high pressures can make the plagioclase more anorthitic with cooling. At low pressures, cooling plagioclase becomes more albite-rich, making it difficult to explain the high anorthite content of the lunar highlands crust. Dr. Nekbasil's work suggests the highland plagioclases could have cooled under higher pressures at depth in the lunar mantle and then been transported to the surface.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/1617.pdf) 

2)  Dr. Pete Schultz gave an amazing talk about the impact that formed South Pole-Aitken (SPA) basin. First he showed spectacular high speed movies of experimental impacts into glass spheres, which demonstrate the disruption and damage that occurs at the antipode of the impact site. These also showed that the antipode of the impact site is not the same as the antipode of the crater for oblique impacts. Next, Dr. Spudis evaluated geological features of SPA , showing that SPA is an oblique impact and that the antipode of the impact site (but not the crater) coincides with the centre of a system of tectonic features related to Procellarum. He thus concludes that the SPA impact would have disrupted the crust under Procellarum, allowing significant melts to form and migrate into the crust. These melts would have differentiated, forming a KREEP layer that was later exposed by the Imbrium impact event. Wow!
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/2416.pdf)

3) One of the themes for the Moon at LPSC this year has been the composition of the lunar mantle. Considering the variety of studies and findings, it is clear that we really don't know what the lunar mantle is made of.

4) Zack Morse is doing some great work mapping the ejecta of Orientale basin on the Moon. This impact has been mapped before, but the last extensive work on this was in 1977. Zack is re-visiting these deposits using more recent data sets like the LROC WAC and NAC images.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/2608.pdf)

5) Dr. P. Boehnke pointed out that only about 50% of all lunar impact samples were heated to temperatures hot enough to reset their Ar/Ar ratios during the impact that formed them. Thus, about 50% of Ar/Ar dates from these samples will show ages that are older than the impact event. This needs to be considered.
(http://www.hou.usra.edu/meetings/lpsc2015/pdf/2745.pdf)

6) That's it. The last talk has been given. The last drink at the bar has been drunk. And the last goodbyes with old friends have been said. Farewell #LPSC2015. You were a great conference for me.
Till next year....

Sinus Iridum - China's Next Stomping Grounds

Clementine mosaic of the near side of the Moon, with arrow pointing to Sinus Iridum.
Image Credit: NASA/JPL/USGS, Annotation by Irene Antonenko

Earlier this week, China's National Space Administration (CNSA) held a press briefing to provide more details about their Chang'e 3 lunar lander, which is scheduled to launch early Monday morning on Dec 2, 2013 around 1:30 am Beijing Standard Time.  That should put the lander on the Moon some time by the middle of December, making it the first spacecraft to execute a soft landing on the Moon in over 37 years. The last man-made lunar visitor to do so was the Soviet Luna 24, which landed in August of 1976.

The Chang'e 3 lander will also deliver a rover, named Yutu, the legendary "Jade Rabbit" companion of the goddess Chang'e.  The last man-made vehicle to roam the Moon's surface was the Soviet Lunakhod 2, which landed in January of 1973 and operated on the surface for 4 months. China's Yutu is expected to roam around the Moon for 90 days and cover about 5 square kilometers of terrain.

The all important landing spot for the Chang'e 3 lander and Yutu rover is to be in Sinus Iridum, or the Bay of Rainbows, on the near side of the Moon.  No spacecraft has ever landed there before. The Soviet Luna 17, which delivered the rover Lunakhod 1, came close, landing over 200 km to the south, on the edge of Mare Imbrium (the Sea of Rains). But even that was a long time ago and over 40 years have passed since then. It is expected that technological advances since that time will make it possible to obtain far better data, allowing us to study the lunar surface in unprecedented detail.

Artist's conception of the Chang'e 3 lander and its accompanying rover Yutu.
Image Credit: Beijing Institute of Spacecraft System Engineering

But, it is also important to study the landing site as much as possible before arrival. Most obviously, this is necessary to ensure a safe site, both for landing and operating on the surface. Secondly, it is important to select a site that is scientifically useful. We have been to the Moon before, so to get the most bang for our buck, we want to make sure we are seeing something different from what we have seen before.  And finally, we want know the landing area as well as possible, so that we can quickly understand and interpret the information we see when we get there. This allows scientists to make critical decisions about where to send the rover next without wasting precious surface time on elementary data analysis.  With that in mind, here is a short primer on the Chang'e 3 landing site.  

Topography of the Sinus Iridium region. Lunar Reconnaissance Orbiter Camera (LROC) data has been processed to determine the topography of the surface. Colours represent elevation, with yellows and oranges representing high topography and blues indicating low lying surfaces. The topography data has been overlain on top of LROM wide angle camera mosaic imagery, helping to highlight the difference between high, rough terrain, and smooth low-lying areas.
     Feel free to explore this region in more detail at the LROC Act-React Quick Map on-line web tool.
Image Credit: NASA/GSFC/Arizona State University

Sinus Iridum is a small lava filled impact crater about 250 km in diameter, which sits beside, and opens into, the much bigger Mare Imbrium, which is also a lava-filled impact structure (up to 1800 km in diameter). The Iridum crater sits on top of an uplift structure (called an inner ring) inside the Imbrium basin and, therefore, must have formed after the Imbrium impact event. The topography of the pre-existing Imbrium impact basin seems to have controlled how the later Iridum crater formed, so that the parts of the Iridum crater that face the centre of Imbrium (to the southeast) are overall lower than the parts that face away. This fact played an important role when both the structures were flooded with basaltic lava, as the topographically lower portions of the Iridum crater were completely covered over, while the higher portions in the northwest remained untouched.

Not all this lava flooded the area at once. It came in relative dribs and drabs. Geologists have used things like surface albedo (or brightness) and the crater counting to show that different parts of the sinus and mare were emplaced at different times, with younger flows covering over older flows in some places, but not in others. These resulting variations can be seen on geologic maps, where the different basalt units are represented by varying colours. In addition, remote sensing studies of the iron content of these basalts also shows that there is great variation between the different flows.

The flooded mare regions of both Imbrium and Iridum are crossed by mare ridges. These are long linear hills that extend for tens to hundreds of kilometers across the mare surface, often running parallell to impact rim and ring structures buried under the mare. It is believed they form when thick piles of basaltic lava cool and contract. This leaves an  upper-most "chill crust", which cooled much earlier and is now too large and loose for the underlying contracted pile, forcing it to bunch up and wrinkle like a table cloth. 

Geologic map of Sinus Iridium and the northwest parts of Mare Imbrium. Purple colours represent materials from the Iridum crater rim. Greens, yellows, and browns represent materials from various younger craters. And pink and grey areas show the different units of mare basalts.
   You can download this geologic map at Lunar and Planetary Institutes Resources portal.
Image Credit: USGS

Map showing the iron content of surface materials in the Sinus Iridium region. Reds to yellows indicate relatively high iron content, while greens and blues show a lower iron content. The high iron regions (red) appear to correspond to the grey mare unit in the geologic map at left.
   You can explore the iron content of the Moon at the USGS Map-a-Planet Explorer web page.
Image Credit: USGS

The exact location where Chang'e 3 and Yutu are going to land is still not known. However, it is likely that these wrinkle ridges will play a role in the landing site. Wrinkle ridges may be able to provide some shade during parts of the lunar day, which can help to stabilize temperatures for the operating spacecraft. Temperatures on the lunar surface reach 390K (117 degrees Celcius) in the day time, which is higher than the temperature of boiling water, and drop  down to 110K (-163 degrees Celcius) at night. The spacecraft cannot function at either of these temperature extremes for prolonged periods of time, so landing in an area where shade is available, at least some of the time during the day, can be very useful for improving spacecraft life.

Personally, I can't wait to see what Chang'e 3 and rover Yutu will discover on the surface of Sinus Iridum. Here's hoping for a successful launch, uneventful journey, and a very happy landing!

Sources:
Lakdawalla, 2013, Chang'e 3 may launch December 1 with Yutu rover, will not harm LADEE mission, The Planetary Society Blogs, Nov 27, 2013.

Schaber, 1969, Geologic Map of the Sinus Iridum Quadrangle of the Moon, I-602 (LAC-24), USGS.

Wang et al., 2013, The Chang E-3 Landing and Working Area Selecting: Based on the Lunar Digital Terrain Model, 21st International Conference on Geoinformatics, DOI: 10.1109/Geoinformatics.2013.6626076

Coming soon: China launches Chang’e-3 lunar probe, China.Org.Cn, Nov 29, 2013.

Why the Far Side has no "Man in the Moon"

Lunar Reconnaissance Orbiter Wide Angle Camera mosaic of the near side (left) and far side (right) of the Moon. Mare Moscoviense is the largest dark lava deposit on the far side of the Moon, where only a few small lava patches can be seen.
Image Credit: NASA/GSFC/Arizona State University

Looking up at the night sky, anyone can see that the near side of the Moon has many gigantic dark splotches. In many cultures, these splotches make up the "Man in the Moon". In others they form a rabbit. So, when the Soviet probe Luna 3 took the first pictures of the far side of the Moon in 1959, we were surprised to see no giant splotches, no Man (or rabbit) in the Moon. Scientists now know that those dark splotches represent large basins that formed when asteroids impacted the young Moon, and which were then filled with massive amounts of volcanic lava. But the question of why there are so few large basins and almost no lava deposits on the far side is still a source of some mystery.

Generally speaking, the distribution of impact basis should be fairly similar on the two hemispheres of the Moon, with both the near side and far side having the same amounts of large, medium, and small impact features.  The size of an impact structure is generally determined by measuring its diameter using the basin's edges, which are called rims. The problem for near side basins is that they are filled with lava, which can often hide important clues for determining where exactly the rim is located, making it hard to measure the basin's size. Also, during the final stages of the impact process, the basin sides collapse inwards due to gravity. For very large basins, this can result in multiple concentric ring structures, where it is not clear which, if any, of these ring structures represents the true basin diameter. So, the question is, are there more large impact basins on the near side because we have incorrectly measured their size?

To answer this question, scientists are using data from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission. Launched in September 2011, the GRAIL mission consisted of two satellites, Ebb and Flow, which were named in a contest (school children from Montana submitted the winning entry). The two satellites measured the gravity of the Moon by tracking the changing speeds and distances between them.  When the GRAIL mission ended in December 2012, the two satellites were purposefully crashed into the Moon. But, during their year-long operating mission, the satellites collected a great deal of data, which scientists are still evaluating today.

Global near side (left) and far side (right) map showing the thickness of the Moon's crust, derived from gravity data obtained by NASA's GRAIL mission. Basins identified in this study are outlined by black circles.
Image Credit:  NASA/JPL-Caltech/S. Miljkovic

One interesting product that has been derived from the GRAIL data is a global map showing the thickness of the Moon's crust. Working together with colleagues from around the globe, Dr. Katarina Miljkovic from the Institut de Physique du Globe de Paris, France is using this crustal thickness map to study the sizes of lunar impact features.  Instead of measuring the diameter of rims to determine a basin's size, Dr. Miljkovic is using the diameter of thinned crust. During an impact, a great deal of material is excavated from the target surface, which then rebounds, allowing the mantle to push up under the crust. Together, this causes the crust to be much thinner under impact basins than in other parts of the crust. And this thinned crust can be used to represent a basin's size. The beauty of this technique is that it doesn't suffer from the same problems as the basin rim measurements. Because gravity measurements see into the interior of the crust, surface lava flows and ring structures are not an issue. The drawback of the crustal thickness technique is that it is generally limited to larger basins since the gravity signature of smaller basins can be difficult to resolve from other features.

Using this crustal thickness technique, Dr. Miljkovic and her colleagues measured all the lunar basins larger than 200 km in diameter.  The results of this work were published just last week in the journal Science, where the researchers reported that basins on the near side are truly larger than those on the far side. The problem is that the total number of craters on the two sides is the same, with just the distribution of their sizes being different. The probability of this occurring randomly is estimated to be less than 2% if both sides of the Moon were subjected to the same population of impacting asteroids. So, what could have happened to put all the big basins on the near side, leaving the far side devoid of large impacts?

There is currently no satisfactory way to get all the large asteroids to target the near side, while the smaller asteroids veer to the far side. For this reason, Dr. Miljkovic and colleagues propose a different reason for the basin size dichotomy. They suggest that the basins on the near side were made by exactly the same kinds of asteroids as those on the far side, but that these asteroids literally made a bigger impact on the near side because it was much warmer than the far side.

 If you recall, the dark splotches on the near side of the Moon also represent the presence of volcanic lava.  Most of the lava is disproportionately located on the near side of the Moon, with 99% of the lava-covered surfaces being found on the near side. This volcanism dichotomy is thought to be a result of two things: 1) a high concentration of radiogenic, heat-producing elements on the near side and 2) a thinner crust on the near side.  Early in the Moon's history, radiogenic elements would have decayed, producing radiogenic heat (though why these elements were concentrated on the near side is still not clear). The resulting heat would have melted parts of the lunar mantle, creating magma which was able to erupt onto the surface because of the thinner crust on the near side.  So, the near side of the young Moon would have been much warmer than the far side, which had a thicker crust and fewer radiogenic elements. These different temperature states on the two hemispheres would have persisted for the whole time the large impact basins were being formed.

Simplified diagram showing how the temperature of the crust affects impact basin formation. Warm crusts experience more rebound during basin formation, decreasing the amount of gravitational collapse. Cold crusts experience less rebound, allowing more gravitational collapse to occur.
Image Credit: Irene Antonenko

To study how the temperature and thickness of the crust affects impact basin sizes, Dr. Miljkovic and her coworkers ran computer simulations. Using exactly the same impactors, they studied how the size of the resulting basin differed for impacts into a warm thin crust (simulating the lunar near side) and those into a cold thick crust (simulating the lunar far side). They found that the crustal temperature had an effect during the last stages of basin formation, when a temporary "transient" basin cavity rebounds and collapses due to gravity. Impacts into a warm crust experienced more rebound, because warm material moves more easily.  The increased rebound means there is less difference in height between the rim and centre of the basin, so less material collapses into the interior due to gravity. This means that outer parts of the basin are not thickened as much by rim material collapsing inward, resulting in a larger diameter of thinned crust. In a cold crust, less rebound means that more rim material collapses into the interior, thickening the outer parts of the basin, making the diameter of thinned crust smaller. Dr. Miljkovic estimates that, for exactly the same impactor, basins in the warm crust can appear to be as much as 2 times larger than their counterparts in the cold crust.

Using this result, the researchers "corrected" the sizes of the near side impact basins, to reflect what they would have been if they had impacted into the cold, thick far side crust. After this correction, the distribution of basin sizes on the near and far sides of the Moon is more comparable, confirming that they were both bombarded by the same population of asteroids. 

Dr. Maria Zuber from the Massachusetts Institute of Technology in Cambridge is the principal investigator of the GRAIL mission. She sums up these findings very well, saying "GRAIL data indicate that both the near side and the far side of the moon were bombarded by similarly large impactors, but they reacted to them much differently.” So now we know why the near side looks so different from the far side. Early in the Moon's history, the near side was much warmer than the far side. This allowed very large basins to form, making huge bowls into which the volcanic lava flowed, so creating the big dark splotches we see today as the "Man in the Moon."

But only on the near side.

Image Credit: Irene Antonenko

Sources:
NASA's GRAIL Mission Puts a New Face on the Moon, NASA News Release, Nov 7, 2013.

Miljkovic et al., 2013, Assymmetric Distribution of Lunar Impact Basins Caused by Variations in Target Properties, Science, 342, p724-726, DOI: 10.1126/science.1243224

The Bizarre Lakes of Titan

This image of the north polar region of Saturn's moon Titan was obtained on Sept 13, 2013, using the Cassini Imaging Science Subsystem (ISS). A number of seas and lakes, consisting of very cold hydrocarbons, show up as dark patches. The image spans about 2000 km from top to bottom, and has a resolution of about 500 m/pixel.
Click here to see an annotated version of the image.
Image Credit: NASA/JPL-Caltech/SSI/JHUAPL/Univ. of Arizona

Besides Earth, Saturn's moon Titan is the only other planetary body in our Solar System that we know has stable liquid seas and lakes at its surface. Planets like Mars may see liquids occasionally erupt from beneath their surfaces, but such liquids tend to quickly evaporate into the atmosphere, and so don't stay long on the surface. But on Titan, scientists have discovered a number of lakes and seas that appear to be stable over long geologic time periods.

The surface of Titan is believed to be made predominantly of water ice. But the temperature at Titan's surface is a very cold 90 Kelvin (about -300 degrees Fahrenheit or -180 degrees C). At that temperature, water ice does not easily melt and so acts more like the planet's bedrock. Titan's seas are, therefore, not made of water, but rather of hydrocarbons, like ethane and methane, which at these temperatures are liquid.

Scientists have been studying the ultra-cold hydrocarbon lakes of Titan for several years, most recently with the help of the Cassini mission to Saturn.  This past September, the spacecraft flew by Titan's north pole and obtained exciting new imagery of these intriguing liquid features using the near-infrared instrument on Cassini's Imaging Science Subsystem (ISS). These images show the lakes as dark patches with very distinctive shapes, having rounded scallop-like edges and steep sides. The surrounding material is also unusual, being much brighter than the rest of Titan's surface, which tends to be dark grey in colour.

The majority of Titan's seas and lakes are found at the north pole, with only a few lakes near the southern pole. It was originally thought that dark terrains at the equator were also liquid hydrocarbon seas. But Cassini images have shown that these are large plains covered in long, linear dunes. Thus, the polar lake areas are truly unusual on Titan. It is thought that their unique environment holds clues to how they were formed, but the exact process is not yet known. Scientists have suggested two possible scenarios: 1) they are Karst terrains, that were formed when the liquids dissolved the underlying rock (or water ice in this case), making surface holes and underground caves in the bedrock, or 2) they were formed by volcanic processes, where magma chambers, which were emptied by volcanic eruptions, collapsed leaving large holes at the surface. In both scenarios, the liquid hydrocarbons would simply have filled up the resulting holes.

The largest liquid body on Titan is Kraken Mare at the north pole.  A sea on planetary bodies is referred to as a mare, the latin word for sea. This dates back to the time of Galileo, who thought the large dark areas on the Moon were seas. We now know that the lunar maria (plural for mare) are not liquid at all, but are solid basalt rocks. However, the name stuck and has been passed on to the liquid seas of Titan. Kraken Mare is quite large by terrestrial standards, spanning 400,000 square kilometers. This is roughly equivalent to the combined size of the Caspian Sea and Lake Superior on Earth, a truly spectacular size!

This radar image of Ontario Lacus, the largest lake in Titan's southern hemisphere, was obtained on Jan. 12, 2010. The lake is about 15,000 square kilometers (6,000 square miles) in size, which is slightly smaller than its terrestrial namesake, Lake Ontario in North America.
Image Credit:  NASA/JPL-Caltech/ASI

Prior to the most recent flybys of Titan, the north polar region hadn't been imaged very well, with only distant, oblique, or partial views being obtained. Part of the problem was that when Cassini arrived at Saturn 9 years ago Titan was experiencing a northern winter, so the north pole was in complete darkness. Since then, summer has been approaching and the northern pole is finally receiving sunlight.  A number of factors have lined up to make the most recent flybys particularly conducive to collecting very good imagery. For one, the sunlight and flyover trajectory have provide a much improved viewing geometry over previous opportunities. Also, with the approach of summer, the thick cap of winter haze that hung over Titan's north pole has dissipated.  And finally, Titan's weather has been unusually cooperative, providing almost cloudless and rain-free skies.

These conditions have also allowed scientists to collect data using the visual and infrared mapping spectrometer (VMS) on board Cassini. By analyzing data collected at a variety of wavelengths, the composition of the surface materials can be inferred. While most of Titan's surface seems to be composed of water ice, sections of the north polar region appear to contain materials that are interpreted to be evaporites. On Earth, evaporites form when shallow seas evaporate, leaving thick deposits of salts behind. Titan's evaporites are thought to consist of haze particles. Liquid methane in the atmosphere dissolves the atmospheric haze particles, which are then rained down to the surface and left behind when the shallow methane lakes evaporate.

We have been referring to these interesting methane lakes and seas as liquid. However, it should be noted that these bodies may not be liquid quite the way that terrestrial seas and lakes are liquid. Radar imagery of these features shows that they are extremely smooth, even at the millimeter scale. This means that they have no waves on their surfaces, not even small ripples. But, scientists calculate that even the slightest breeze should produce substantial waves, because the mixtures of ethane and methane that make up these bodies are less viscous than water.  So, it may be that these lakes also contain other hydrocarbons which make the ethane/methane mixture much more viscous, giving it a thick consistency, like that of tar or mud.

Bizarre lakes, indeed!

Sources:
JPL's Cassini Featured Image, 2013, Bird's Eye View of the Land of Lakes.

JPL's Photojournal, 2013, Titan's Northern Lakes: Salt Flats?

Hecht, 2011, Ethane lakes in a red haze: Titan's uncanny moonscape, NewScientist, 2820.

Lorenz, 2010, Winds of Change on Titan, Science,  V329 (5991), 519–20, doi:10.1126/science.1192840.

The Fun of Geologic Maps!

Excerpt from the geologic map of the western Winston-Salem area in
North Carolina, Virginia, and Tennessee. See the full map below, or
download it from the USGS  National Geologic Map Database.
Image Credit: USGS

Friday October 18th, 2013 is Geologic Map Day. No, really, such a thing does exist. It was founded by the US Geological Survey (USGS), the American Association of State Geologists, and the American Geosciences Institute in order to raise public awareness of the significant contributions geologic maps make in science, business, and public policy. To learn more, check out the Geologic Map Day website, where they have links to lots of neat stuff, such as geologic maps (of course), FAQs, and activities. Warning, this site is very US-centric. However, most countries have their own geologic branches of the government, which often provide on-line access to geologic maps. These can usually be found with a quick Google search. For example, the Geological Survey of India has links to a number of geologic maps throughout that country.

I think geologic maps are fun because they are so colourful. Unlike road maps, which link places with a network of lines, geologic maps look at areas. Each area is defined by the type of rock that is found there, and this rock type is shown on the map by a specific colour. This way, it is easy to tell at a glance which areas of a map have the same rock types.... and which ones don't. A legend is used to tell the map user what kind of rock each colour represents. Other geologic information, such as where faults are found, is represented by symbols, which are also explained in the legend. Some maps even come with cross sections, which show you a side view of the map at certain points, as if you had sliced the earth open like a cake and taken a look from the side. And some maps also have several paragraphs of text, explaining what happened in the mapped region, from a geological point of view.

Geologic map from the western Winston-Salem area in North Carolina, Virginia, and Tennessee, prepared by Rankin, Espenshade, and 
Neuman in 1972. The full map can be downloaded from the USGS  National Geologic Map Database.
Image Credit: USGS

Most people think of maps as something we make for places on the Earth. But we have been studying planets long enough that we have a fabulous assortment of maps, including geologic maps, for the other planets. The Lunar and Planetary Institute lists a bunch of links to planetary maps (and images) for the Moon, Mars, Venus, and Mercury on their Resources page.   My favourite is the Geologic Atlas of the Moon, which has links to on-line versions of every geologic map of the Moon published by the US Geological Survey.  Here you can find geologic maps for the Apollo landing sites, other regions of interest, and the entire Moon, divided up onto smaller segments.

This geologic map from 1971 (top) shows the Hadley Rille region of the Moon, where the Apollo 15 mission landed. The red lines overlaid on the map show the traverses that the astronauts undertook (determined from recent image data). This kind of information tells us that the astronauts saw a variety of geological regions on their traverse. They started out in flat mare terrain. One of their traverses skirted the ejecta of a young impact crater (olive green). Another traverse crossed the debris slopes (olive brown) of the Apennine Mountains (brown) to venture into the hills themselves. The third traverse cut through a crater field (pink), which was most likely formed by the ejecta from a much bigger crater well off the map, and then headed into the Apennine Mountains (brown) again.  In contrast, the Lunar Reconnaissance Orbiter Camera (LROC) image (bottom) does not provide this much information. The Apollo 15 traverses, shown in red, were determined from very high-resolution LROC images.
View the full map, with legend and explanations at the Lunar and Planetary Institute's Hadley Rille map page.
Explore this area of the Moon in more detail using the ActReact QuickMap Web Interface.
Examine the Apollo 15 traverses for yourself at the LROC Apollo 15 Traverse Page.
Image Credit: USGS (Map), NASA/Goddard/Arizona State University (Image and Apollo 15 traverse), and Irene Antonenko (compositing).

You can also find geologic maps for other planetary bodies in our solar system. Many haven't been studied long enough to have geologic maps made of the entire surface, but there are sections that have been mapped. Again, a quick Google search can find you lots of interesting tidbits. On a whim, I searched for "geologic map of Titan", which is one of Saturn's moons, and found an amazing little geologic map and article on the Selk crater of Titan, from The Planetary Society. Seriously, you should go check it out!

So, I hope this article has piqued your interest and inspired you to go check out some geologic maps, whether they are of Earth or any other planetary body, and celebrate Geological Map Day.