My Astronomy Class - Lunar Crater Anatomy

[Ad Astra]

With the Moon waxing this week, why not try your hand at really exploring some lunar craters along the terminator? (That's the line that seperates light from dark on the lunar surface.) Lunar craters can show a surprising variety of features and the craters themselves change as they age slowly over billions of years.

Download the 'One-Page-Easy' activity and give it a shot. See if you can find, sketch, and then map the location of the features you observe. Bonus points for those who can later positively identify the features they've sketched using a lunar atlas!

Give it a go and let us know how you do... Comments and questions are always welcome.

Dan

Lunar Crater Anatomy.doc

[Ad Astra]

My students took this one on tonight with the gibbous moon. Tycho was clear and there was a wonderful view of Gassendi and mare Humorum. We had the C-11 out and the kids followed along on the 150p f/8 dobs and 7x50 bins. I will scan a few of the best and (with permission) post them here. They make a decent mark to shoot at, as none of them have been at astronomy for more than 5 weeks... and they have the added handicap of having me drone on at them for an hour a day!

All of the kids found that translating what they were seeing into something comprehensible on the page to be very challenging. I have found however, that even simple sketching can be accurate and exciting, but it requires patience at the eyepiece, and some discipline in the act of observation. You cannot possibly record anything accurately if you do not trouble to observe it closely and accurately. It all amounts to practice - and if you LOVE IT like most of us do, this isn't onerous, it's heaven. For many students, astronomy becomes just another thing to learn to do like kicking a football or solving a quadratic equation.

For me, as an astronomer; I want the kids to dig in and revel in the deep mystery and endless inquiry and discovery and the joy that transcends learning. But as a teacher, I have to cast a wider net than that. I have to challenge people like them (and you lot on SGL!), to dig in to the science a bit, but not forget that I'm here to inspire and create people with practical thinking skills. I have to engage and entertain, but keep focused on the fact that everything I do has to be relevant - hopefully relevant enough to help them get and keep a job after their done with school.

What we do here on SGL is important. When I share lessons here, you folks help me hone and shape the curriculum, and I in turn, share it round the world with other teachers and parents. Generally, when things work well here, I know I can count on them in the classroom, too. When they don't (and sometimes the silence is deafening!), I know I've got to go back and rework the exercise. It's all good - in the end, you lot help me to be a better educator... and then the kids win, too.

Thanks,

Dan

[Mr Q]

With the Moon waxing this week, why not try your hand at really exploring some lunar craters along the terminator? (That's the line that seperates light from dark on the lunar surface.) Lunar craters can show a surprising variety of features and the craters themselves change as they age slowly over billions of years.

Download the 'One-Page-Easy' activity and give it a shot. See if you can find, sketch, and then map the location of the features you observe. Bonus points for those who can later positively identify the features they've sketched using a lunar atlas!

Give it a go and let us know how you do... Comments and questions are always welcome.

Dan

Lunar Crater Anatomy.doc

Sorry, with no atmosphere (wind or rain), the craters have not changed in billions of years. As the solar system ages (to its recent age), the debris impacting the Moon and other members of the system has dramatically dropped off with the "cleaning" of the system's left over debris from when it was young. They can change appearance when another object impacts on an existing crater or near it but since we have only been observing it with optical aid for a few hundred years, no objects have done such changes to any crater on the Moon. That makes it an amazing event when we got to see a comet impact on Jupiter but Jupiter being so much larger than the Moon and such a bigger target, who knows...some day (or night) one of us may witness such a rare event

As for the school activity, sounds great and I'm sure the activity will foster many kids into the hobby and who knows,,,perhaps a great astrophysicist may be a end product in one of them

[BiG JiLM]

It was a terrific night here in mid/sth UK (once the high cloud had shifted off) for the moon, esp the terminator Humorum.. and was the big crater at the terminator Gassendi then? I find it actually quite hard to differentiate one crater from another, even with a decent small 'stargazing with telescopes' book. Can you say more of the 'One-Page-Easy' is it a program thing? I think your kids are probably at a better level than me- Gibbous is a word Id never even heard of before.

It must be very rewarding teaching kids astronomy with a good telescope- you must have a major advantage in that it doesnt get cold I assume like here over next 5 months: I dont think many kids' attention would last more than 5 mins here.

[Astronut1982]

Mr Q,

I think you'll find that the craters do change over long periods of time & that the Moon does have an atmosphere albeit an extremely thin & almost non existent one.

One of the ways in which the craters change is that the crater rims flatten out although at this present time, I'm unable to remember the mechanism by which this takes place & I can't find my Open University course book to find that out but I did learn that from there. Another is that they also darken as they age which is why the more recent (astronomically speaking of course!) craters are brighter than the older ones, I believe that this is due to accumulations of dust but I'm not 100% sure that this reason is the correct one (I'm just sure that I read it somewhere).

Ad Astra,

Thanks for the document, the next night that it is clear (goodness knows when that will be!) I will have a go at it. I've had a look at some of your other coursework before & it looked very good & I'm positive that your students would find them very interesting.

Jeff

[Mr Q]

Astronut - My point was/is that in the few hundred years we have been able to observe the Moon telescopically, there can't be any changes we can see (especially in our lifetimes) since the changes you mentioned occur over hundreds to thousands of years. The only changes I'm aware of that you mentioned is the change in reflectivity of the relatively flat areas which also takes too long for us to observe them. Yes, we can see the results much after the fact, since some areas are more reflective (of sunlight and earth shine). I'm sure changes in the Moon's outer crust have also changed it's appearance but enough for us to see within a few hundred years?

I just hope the original poster comment on the craters changing appearance will not encourage young observers to expect to see any in their lifetime because even with photographic record keeping, they will be very disapointed.

There was a recent mission to crash a probe into it's surface and examine the dust plume it made but I'm pretty sure the event was not big enough in size to be seen from here on Earth but if anyone has any further input on this event, I'm eager to hear if anyone seen the event happen telescopically.

[Astronut1982]

Thats a fair point Mr Q although the OP did state that the craters change slowly over billions of years so I wouldn't think they would be expecting to see any changes themselves.

However, by photographing, sketching & documenting what they are seeing on the lunar surface they can help to show the changes that have taken place over the years so that those who will come long after after us can see the changes that have taken place by studying the information collected by his students & others who are doing similar things.

Jeff

[Ad Astra]

Hi Big Jim,

"One-Page-Easy" is part of the way I write curriculum for my classes. I've found that if I put an introduction, instructions, and a place for a response (data, sketching, etc) - and it still all fits on a single page, then I have made the lab simple enough, short enough, and easy enough that any begining astronomer could happily spend an evening enjoying the exercise, and a high school student could zip through the exercise in under an hour and still do a creditable job.

When I post an activity here, I've usually already tried it out with my classes here in California. When I see what kind of success that my own students have, then I'm ready to release it (usually with a few tweaks and adjustments) to everyone on SGL. I'm very keenly aware that my students have an instructor to hand and can ask for help or clarification when they need it - the best you lot can do is post a reply or PM here and wait for an answer.

As for your crater dilemma - that's just a matter of learning the lay of the land. Instead of trying to match your view to a map - try doing it the other way round. Look at your map and pick out 3-4 large and prominent craters, and then see if you can find them on the Moon. Once you get to know landmarks like Tycho, Copernicus, Gassendi, Clavius and a few others, you will start to be able to identify the smaller ones nearby by thier relationship to the larger, easier to find members. This way you also limit your task to a handful of large, easy targets - you're not trying to look through the eyepiece and identify everything you see (a much harder task!).

One last thing, friend -- I think you vastly underrate both yourself, and the kids in both our countries. I teach in a relatively poor, rural community where most families are low income, many kids are still learning English, unemployment is pushing 25% locally, and many of our parents haven't finished high school themselves. Even so, the kids amaze me every day by what they are able to achieve when they are given a sufficient challenge to measure themselves against and proper guidance from the adults in their lives.

If they can, then you can, too; and when you learn how, turn around and teach a child. Both of you will benefit immesurably.

Cheers,

Dan

It was a terrific night here in mid/sth UK (once the high cloud had shifted off) for the moon, esp the terminator Humorum.. and was the big crater at the terminator Gassendi then? I find it actually quite hard to differentiate one crater from another, even with a decent small 'stargazing with telescopes' book. Can you say more of the 'One-Page-Easy' is it a program thing? I think your kids are probably at a better level than me- Gibbous is a word Id never even heard of before.

It must be very rewarding teaching kids astronomy with a good telescope- you must have a major advantage in that it doesnt get cold I assume like here over next 5 months: I dont think many kids' attention would last more than 5 mins here.

[Ad Astra]

Hello friends,

I think I must have expressed myself badly again. Let me try to clarify, if I can. My students are studying the Moon just now, and we will discuss theories of the Moon's origin, and evidence for and against those theories. Every theory must account for the evolution of the lunar surface over time (billions of years of time with the rate of impacts decaying much as half-life decay affects a radioactive sample). Because there is no air or water on the lunar surface, you can see evidence of changes in the surface quite clearly even though the actual event occured billions of years in the past. One has to remember that the model for lunar geologic change is a catastrophic model - not a gradualism. Change here occurs in sudden, violent bursts, followed by long periods of almost perfect preservation of the status quo. Here are some samples of geological change that you CAN spot and appreciate on the Moon with a modest (150mm dob) telescope or better.

1. Crater deformation. Craters begin life as narrow, conical depressions, but severe stresses in the crust cause this structure to quickly collapse - steep walls slide inward and the crater basin fills and levels with debris. Late crater wall collapse can be seen and evidence of large blocks of basalt from the rim sliding and pushing a rubble field ahead of them which fans out on to the crater floor. Lava filled craters like Plato show this sort of phenomena very clearly.

2. Lava flooding, and flood sequencing. Craters which border maria often show evendence of rims that are overwhelmed by lava flooding from the maria. Sometimes if the local solar angle is low enough, you can even see ripple structures which clearly evidence the direction of flow. Ripples from a small source (like a crater wall breach) show characteristic bow-like structure as the liquid wave front spreads out from a narrow source to a wide area. Lava colour and flow lines often make it clear which flow happened first, even if we cannot definiatively date them from the eyepiece.

3. Crater saturation, crater erosion. Especially in the highlands of the southern lunar hemisphere, you can see evidence of ancient crater basins that have been overwhelmed by subsequent (generally smaller) impacts. A good map is needed here, and you must choose the day (and local solar angle) carefully, but ancient structures can be revealed - and at the same time the scale of impact and bombardment can be appreciated.

4. Central mounts in craters. A central mount occurs when an impactor punches deeply enough into the lunar interior to cause a rebound - effectlvely, the impact energy is sufficient to make the lunar surface act like a liquid for a very brief time. Look at a high speed photo or film of a water drop falling into a liquid surface and you will see much that resembles crater structure! It is instructive to compare central mounts in flooded craters (such as Gassendi) to those of unflooded craters (such as Tycho).

There are many more examples - but these will serve to get you started, and help you to enjoy your views of the moon even more.

Cheers,

Dan

Astronut - My point was/is that in the few hundred years we have been able to observe the Moon telescopically, there can't be any changes we can see (especially in our lifetimes) since the changes you mentioned occur over hundreds to thousands of years. The only changes I'm aware of that you mentioned is the change in reflectivity of the relatively flat areas which also takes too long for us to observe them. Yes, we can see the results much after the fact, since some areas are more reflective (of sunlight and earth shine). I'm sure changes in the Moon's outer crust have also changed it's appearance but enough for us to see within a few hundred years?

I just hope the original poster comment on the craters changing appearance will not encourage young observers to expect to see any in their lifetime because even with photographic record keeping, they will be very disapointed.

There was a recent mission to crash a probe into it's surface and examine the dust plume it made but I'm pretty sure the event was not big enough in size to be seen from here on Earth but if anyone has any further input on this event, I'm eager to hear if anyone seen the event happen telescopically.

[Mr Q]

Jeff (and the OP) - My error in missing the OP's "billions of years" part of his statement.

As for recording present observations for future people to refer to (eons from now), how would these records be kept?

My responses to the OP's statement was to clear up any notions of the kids wrongly expecting to see any changes in their lifetimes by missing the "billions of years" concept as I did. Besides, what detailed records (a photo would be needed) in the past hundred years have shown any changes? Maybe the word "theory" included would have made the statement clearer in regards to crater changes?

All this aside, I do commend the OP's efforts to advance astronomy knowledge in youngsters, as hopefully this site does.