Let’s continue on our journey to the Moon. Last week we talked about the physical characteristics of the Moon, its appearance in the sky and how it interacts with the Earth. This week we’re going to take a look at how scientists have expanded our understanding of the Moon. From ancient astronomers using nothing more than their eyes and the first telescope observations of Galileo to the exploration by robotic spacecraft. And of course, the first tentative steps by the human explorers of the Apollo program.
Before we went…
- Aristotle, Galileo and the Moon — Galileo Project
- Lunar mare — Absolute Astronomy
- Lunar Basalt — Wiki
- Franz von Paula Gruithuisen — Internet Encyclopedia of Science
- Finding craters on Earth with Google Earth — Google Earth Blog
- Nomenclature of Lunar craters — NASA
Early Missions to the Moon
- NASA’s timeline of lunar missions
- Russian Luna 1 ( 1959 flyby), Luna 2 (1959 impact), Luna 3 (1959 probe)
- US Pioneer 4 (1959 flyby)
- Ranger missions (1961-1965)
- Huygens probe to Saturn’s moon Titan
- Surveyor missions (1966-1968)
- Apollo missions overview (1968-1972)
- Book: A Man on the Moon by Andrew Chaikin
- Movie: From the Earth to the Moon
- Movie: Apollo 13
- Movie: In the Shadow of the Moon
- Movie: When We Left Earth
Subsequent robotic Moon exploration
- Hitan (1990)
- Clementine (1994)
- Clementine Color Mosaics of the Moon
- Lunar Prospector (1998)
- Smart-1 (2003)
- The Magic of Ion Engines — ESA
- Kaguya (SELENE) 2007-present
- JAXA’s Kaguya site, includes Hi-def movies of the moon
- Chang’e 1 2007- present
- More on Chang’e 1 from the Planetary Society
Transcript: The Moon, Part 2 – Exploration of the Moon
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Fraser Cain: Let’s continue on in our journey to the Moon. Last week we talked about the physical characteristics of the Moon, its appearance in the Sky and how it interacts with the Earth.
This week we’re going to look at how Scientists have expanded our understanding of the Moon from ancient Astronomers using nothing more than their eyes and the first telescope observations of Galileo to the exploration by robotic Spacecraft.
And of course, the first tentative steps by human explorers of the Apollo Program. So, let’s go right back to the first discoveries that humans have made about the Moon. I guess in the beginning we just had eyes.
Dr. Pamela Gay: Well and initially it’s not like we didn’t know the Earth had a Moon. It is probably one of the first things people noticed – Oh, there’s a giant bright object in the Sky that changes phases.
Fraser: Who discovered that?
Pamela: Yeah, I don’t know his name. [Laughter] It’s not in Wikipedia. But the main record that Western thought bases itself on in studying the Moon goes back mostly to Aristotle and Plutarch. Aristotle in looking at the Heavens saw all of the heavenly bodies as perfect spheres because well, the sphere is the perfect shape therefore everything in the Sky must be the perfect sphere.
However, when you look at the Moon it is mottled in color. There’s the ‘Old Man’ or the ‘Rabbit’ in the Moon depending on your cultural perspective and many other shapes as well.
When Plutarch looked up, what he saw instead was that the dark places were corrupted. They were chasms, they were craters (well they didn’t know what craters were back then) they were pits; they were cut-aways from rivers. They were places where the Sun wasn’t able to reach the bottom in and instead we’re looking into deep shadow.
So, we have these two completely different views. Aristotle going: spheres, perfect wonderful it’s in the heavens. Plutarch going: no, corrupted body, deeply shadowed, large chunks missing that the Sun can’t reach the bottom of. So there is this wonderful dichotomy. Most people listened to Aristotle.
It wasn’t until Galileo and his “well let me look up with the telescope” way of looking at the Universe that we started to realize that for certain the Moon wasn’t a perfect sphere.
The Moon had mountains; it had these weird round pits. It had all of these different surface features and he was able to say for certain that the two different colors were two different surfaces. That’s kinda cool.
Fraser: And how are they two different surfaces? What’s the difference between the parts that are dark and the parts that are lighter from our point of view?
Pamela: We didn’t know that for a long time. He was simply able to say that the dark stuff is not a giant pit. He was able to say that’s just a surface. It wasn’t until we went and started exploring it that we were able to confirm for certain that the dark stuff is basalt, it is lava. It’s melted rock that has been cooled and solidified. It’s either from actual volcanic type stuff or just more oozing of lava out through the surface or from re-melting of the surface during cratering. The light stuff is in the inner highlands, it’s just rock.
What’s kind of cool to me is we look at the Moon – and having grown up learning about Asteroids at about first or second grade, the difference between a Meteor a Meteorite or a Meteoroid – we look at the Moon and see the round spots as craters. But it wasn’t actually until the 1820s that a man whose name I’m going to horribly mispronounce, Franz von Paula Gruithuisen got the idea that maybe these things were Meteor strikes. He thought maybe these round pits with crater walls are actually crater marks on the Moon.
Fraser: And there’s an object like that here on Earth, the Meteor crater in Arizona which looks very similar.
Pamela: Right and now that people are starting to peer through all sorts of satellite imagery there are major craters that look like craters all over the planet Earth.
There are actually all sorts of projects in Google Sky or Google Earth as the case may be, to try and locate other potential crater walls scattered around the Planet. And that’s just cool our Planet is pock-marked too.
Fraser: Well, after Galileo you can imagine that every Astronomer worth their salt was pointing their telescope at the Moon when they weren’t discovering the Rings of Saturn [Laughter] or something. Beyond that what kinds of discoveries started to pour out?
Pamela: Mostly we were happily mapping the surface of the Moon, naming things in all sorts of different ways. There were many different naming conventions that were used. The one that was eventually settled on is the idea that large naked eye blobs on the surface are named as seas (mare). The little spots that you can only see through telescopes which we now know are craters are named after philosophers and I just like this dichotomy.
Since then we’ve broken it and so there’s shackles and craters and things like that. It wasn’t until 1753 that we realized that the Moon doesn’t have an atmosphere. Up until then people had randomly thought maybe there was life on the Moon.
It was actually Plutarch who started that idea. As early as essentially the beginning of Western Civilization there was the concept that maybe there was life on the Moon. Then in 1753 we realized no, there’s not, there’s no atmosphere there. Then as I said in the 1820s we realized that the craters were made by Meteor strikes.
From then on, we basically mapped and that was all we could do without having any solid compositional data. Even with the mapping we could only map a little more than fifty percent of the Moon because the Moon, as we talked about in the last episode is tidally locked to the Earth. We can only see one side of it.
The Moon has what we call vibrations. It vibrates a little bit and we can see around the edges a little bit as it oscillates slightly. But we mapped the one side we could see really, really well. Then we waited for manned Space flight and unmanned Space flight to get invented so that we could start looking at other things as well.
Fraser: So then fast forward, I mean beyond just mapping, [Laughter] fast forward to the first attempts to actually reach out with Spacecrafts and explore the Moon. So what were the first attempts to get to the Moon?
Pamela: Well, back as early as 1959 actually we were flinging things at the Moon. It was initially mostly the Soviets flinging things. There were three different Luna missions, one, two and three, conveniently named in 1959 as well as one Pioneer mission from the United States.
The Luna missions were off to first take pictures of the Moon and second to go land on the surface and find out what the surface is made of. So the first mission was intended to land on the surface – well impact on the surface – landing is a bit strong of a statement. But it missed. It flew by, took pictures and then it kept going.
It was actually the very first object to end up orbiting the Sun instead of the planet Earth. Then after that the United States launched its Pioneer mission. That again was a fly-by, took pictures, and happily explored the environment. It did a radiation experiment and then we went back to the land of the Luna missions. We had Luna 2 which did manage to successfully hit the surface of the Moon and then
Fraser: It landed.
Pamela: It landed.
Fraser: The hard way [Laughter]
Pamela: But they intended to land the hard way. So it was alright.
Fraser: Right, that was all part of the plan.
Pamela: It was all part of the plan and then finally, Luna 3, toward the end of 1959 allowed us to see for the first time – this was a Soviet mission – it returned the first ever pictures of the back side of the Moon, the unknown, the dark side of the Moon that really does get lit up as much as the front. So finally in 1959 we were able to see this mysterious other side of the Moon.
What’s cool is the back side of the Moon is radically different. It is cratered completely differently. It has much, much less lava on it so it’s coloration is very different. And so that was just a fabulous moment. Then no one went back to the Moon for a year.
Fraser: [Laughter] Right, now I’m assuming that you’re glazing over all of the failures, all of the rockets that exploded on the pad and crashed into the atmosphere and so on.
That’s fine, we don’t want to repeat – we had a lot of complaints on the Mars episode about the failure after failure so we’ll gloss over the failure after failure.
Pamela: But the thing is those four missions I just named, according to the NASA Lunar Exploration Timeline which does list lots of failed missions – those were the only four.
Yeah, Luna 1 missed and kept going but it still returned data. So the Moon doesn’t have quite the same curse that Mars suffers from.
Fraser: Right, okay so we’ve gotten to the point that we’ve seen the far side of the Moon for the first time. What about landing?
Pamela: There was a gap. Here’s where the United States started to get involved again with things that didn’t like to fly in the 1960s with the Ranger program, it was not one of America’s more successful programs. It had two attempted test flights in 1961 and both of them failed.
Then we had in 1962 an attempted impact and we missed. Ranger 4 did successfully find and crash into the surface. It was designed to transmit pictures. It was able to do this for about 10 minutes prior to impacting the surface.
What’s kind of cool is one of our goals was to basically shake the Moon to collect data on what happens when you have a rough landing. This is sort of like when we landed the Huygens Probe on Saturn’s Moon Titan. We wanted to find out what the surface is like.
One way to do that is to land a bit more violently than you might like and Huygens didn’t really do that. But then to see what shakes, what is the impact like, if you have a nice slow deceleration then you landed on something squishy.
If you have a bit abruptive landing that means you landed on something a bit more solid than you might have liked. So there are reasons to fling yourself into the surface of a foreign body.
Fraser: Well the surface of the Moon is a bit of a mystery, right? I mean they knew that it was covered with dust probably from billions of years of micro-meteor impact but they didn’t really know how hard this stuff was going to be.
Pamela: Right. This is the problem with the Regula. The Moon is constantly being barraged by micro-meteors. Fred Hoyle was one of the people who put forward the idea that “yeah you’re going to land and you’re just going to sink into the dust.”
We eventually ended up building an entire series of missions – the Surveyor missions – that started launching in 1966 with a goal to land purposely, land softly and send back data. They had Solar Arrays, TV cameras, all the nice little things including arms to dig into the surface. You can see these as kind of the baby precursor version of our current Mars Polar Lander.
These happy little tiny robots that are really quite darling. They look like tripods that have been overburdened with electronics. These little robots successfully landed in many cases and were able to send data back to the planet Earth.
So, now instead of impacting the surface, we’re purposely landing on the surface. We did our first purposeful landing May 30th of 1966; tried again in September – didn’t work so well – kept trying and these were the precursors to the Apollo landings.
Fraser: Right, so these were the ones that really sent out the first pictures of the surface of the Moon, tried to dig around and see what the surface was like, but you already kind of mentioned the next big plan which was the Apollo mission. Maybe rewind a bit and talk about that.
Pamela: This all started with John F. Kennedy from my home state of Massachusetts. When he became president he wanted to give our Nation a vision and part of that vision was violently beating the Russians to the Moon (well, not with violence but peacefully) beating the Russians to the Moon.
He put this idea forth very eloquently in his speech where he said: “We choose to go to the Moon. We choose to go to the Moon in this decade and to do other things. Not because they are easy but because they are hard. Because that goal will serve to organize and measure the best of our energies and skills because that challenge is one that we are willing to accept, one we are unwilling to postpone and one which we intend to win and the others too.” He goes on it’s a really cool speech.
Then they start throwing resources at it. That was the cool thing, NASA didn’t have a lot of money but they did a lot of deficit spending. Nowadays I don’t think NASA would be quite so allowed (not even a strong enough a word) no one would allow NASA to keep going if they went into the same amount of deficit spending that we had during the Apollo era.
They were able to in less than 10 years go from not really being able to get things consistently to the Moon to landing human beings on the Moon and returning them with a lot of rocks. Rocks don’t weigh small amounts and that’s just cool.
We accomplished an amazing amount of stuff – all of this before I was born. The last crewed landing on the Moon occurred in December of 1972, more than a year before I was born. This is I think part of why people of my generation are a bit, yeah NASA, do something now please because we haven’t seen any really cool accomplishments.
No one has landed on the Moon in our lifetime. But in that one brief wonderful deficit spending period of time, NASA went from missing the Moon to successfully landing and returning people.
Fraser: I don’t think we have the time in this episode to really go into the details of how the Apollo program worked but there are some wonderful documentaries and TV shows and movies that you can watch that will show you them. “From the Earth to the Moon” is amazing.
Pamela: It’s a must see. I make my students watch it.
Fraser: Apollo 13; there’s a new one by the Discovery channel which is “When we Went to the Moon”. There’s a lot of great material out there to be able to sort of bring you up to speed on all of the missions. Yeah, “From the Earth to the Moon” I think is the most entertaining, comprehensive accessible look at the Apollo mission.
So, if you’re older and you want to get your kids into the Apollo missions, that’s the show to watch. They really make it quite entertaining, very much in the style of Apollo 13 as well. It all kind of mixes together quite well.
Pamela: What’s really cool about this stuff is how much history is involved in it. So, if you have a friend who thinks, yeah science, I don’t care, but is interested in politics and history, the Apollo mission is the way to suck them into science as well.
We’re dealing with personalities, how to fund all of this, dealing with everything else that was going on in the world at that time. It’s just very fascinating to watch. While America so far is the only nation that has managed to successfully get people to the Moon and back, the Soviets also helped returned rocks. Returning rock – if you’re not into rocks and I admit to not being into rocks – really doesn’t sound that all exciting because they’re rocks.
The thing about Lunar rock is you can use it to start dating different surfaces. So by sending people to different areas on the Moon and by sending Lunar Return Landers to the Moon, we were able to gather rocks that we could bring back and we could use carbon isotope dating to say, this region that has very few craters is this age. This region that has this number of craters is this age.
Using the rocks gathered on the Moon and assuming that impact crater rates are fairly consistent across the Solar System (which we think is a reasonable thing to assume) we’re able to make rough estimates of the ages of all the rocky non-weathered bodies in the Solar System. That’s just really cool.
Fraser: So, July 19, 1969, Neil Armstrong and Buzz Aldrin step out on the Moon for the first time and stay out there for a few hours and come back. Several missions after that leading up to 1972 I think Gene Cernan was the last person to walk off the Moon.
Humans haven’t set foot on the Moon since then. But that’s not the end of their exploration of the Moon. There have been missions ever since and right now. So, let’s not get stuck in 1972 [Laughter] let’s get going and talk about some of the other missions.
Pamela: The NASA timeline which includes everything else – it’s on the NASA.gov website shows how in January 1973 there was a Soviet Rover. In 1974 there was a Soviet Orbiter and Lander.
In 1976 there is another sample return mission. Then the Moon gets ignored until 1990. Through pretty much my entire child adolescence there was nothing to do with the Moon anywhere.
Fraser: Right it’s all about the Space Shuttle.
Pamela: It was all about the Space Shuttle and the Space Shuttle is cool but it only goes 300 miles up which in terms of exploring the Universe is nowhere.
Fraser: Fine, the Voyagers.
Pamela: The Voyagers were awesome. They were out on the edge of the Solar System. They were what got me excited in Astronomy.
Fraser: Me too.
Pamela: But, we ignored the Moon and then the Japanese got involved. They sent this wonderful little mission that was called Hiten – I’m sorry I’m going to mispronounce things because they don’t teach you about this in graduate school.
It translated into Flying Angel. A wonderful little mission that went out and it was taking pictures and basically re-opened the door. It got us back exploring the Moon a second time. This wonderful little Japanese craft was mostly out there looking at dust. It checked out the Lagrange Points.
It eventually ran out of fuel and they crashed it into the Moon which doesn’t sound all that exciting. But when you hit things into the surface of the Moon you can make the Moon vibrate. The way they vibrate allows us to start probing the density of the Moon, probing how it reacts to different things.
The Apollo Astronauts left mirrors on the Moon so when we hit the Moon with things like this cute little Japanese Spacecraft it makes the Moon vibrate and we can see those vibrations in laser light reflected off these mirrors. That again is just kind of cool. So, in 1990, the Japanese re-opened the doors to Lunar exploration.
A few years go by, nothing much happens and then America gets back in the game. We go out and start doing detailed imaging again. Here we have the Clementine mission. This is the point at which the United States starts thinking again about going out and figuring out how do we get people back on the Moon.
Mapping the Moon in great detail is one of the first ways to do this. The Clementine mission had lots of different ways of imaging the Moon. It had a laser imaging detection and ranging system. They were flying over the Moon bouncing laser light up and down which allows you to get very accurate altimetry of the Moon, very accurate altimetry of the Moon and very accurate measurements of the rise and fall of the surface.
They had radar, high-resolution cameras, they had ultra-violet invisible cameras and they were even able to detect charged particles coming up off the surface of the Moon.
Fraser: Yeah, Clementine REALLY mapped the Moon to within an inch of its life. [Laughter] Nothing had ever been mapped at that level, to that detail; like just REALLY amazing contour maps.
I was actually doing some work on this recently and all of the Clementine maps have been turned into these really amazing mosaics. You can search for like Clementine, Moon Map or Mosaic on Google and you can get access to these really detailed maps that have been stitched together of the images that Clementine took of the Lunar surface. It’s quite amazing.
Pamela: They weren’t the perfect images. They weren’t high enough resolution that we could start looking for ice down in the bottoms of craters. We’re going to do better in the future. But it was a great start to getting back.
The resolutions were less than about 5 meters when the Orbiter was in its closest approach. It was great work. We were able to get great measurements of altitude of different surfaces. It was a wonderful way to get back and get started and start figuring out this little body so close by one more time.
From Clementine we’ve gone on to there was a Lunar Flyby with a mission in 1997 – not so exciting, I’m going to move on. Then we had Lunar Prospector in 1998 which was another mission to go out and in this case it was looking out in all sorts of ways that you wouldn’t think to look.
We had a Gamma Ray Spectrometer, a Neutron Spectrometer, and an Alpha Particle Detector that detects high energy Helium Nuclei flying off. They had a Doppler Gravity experiment. They had all sorts of different ways of looking at it other than through photography.
This allows you to start probing for what’s below the surface. It starts allowing you to probe for how the surface reacts when it gets hit with a Coronal Mass Ejection and flares from the Sun. All of these things start to give us hints of the chemistry of the Moon at the density structure of the Moon. This allows us to start trying to figure out is there water on the Moon.
Fraser: The goal here with Lunar Prospector is just with its name, to beyond mapping the surface but to try and map the locations in quantities of chemicals and minerals on the surface of the Moon.
Are there vast stockpiles of water ice? What elements are there? Are there elements that reacted with other chemicals in the past? You really just get a sense of what’s there and where it is.
Pamela: So the Neutron Spectrometer is perhaps one of the most important instruments for this search for water. Using it, Scientists were able to detect the Neutron emissions that you would expect if there’s water hiding under the surface.
The frustration we’re having is as we look for it with other missions we can’t directly image it and we talked about this in the last show. So, any water there is on the Moon appears to be trapped in different things.
According to the Lunar Prospector data, there should be about 3 billion metric tons of water ice in the polar crusts of the Moon. Now we just need to figure out how to get to it.
So Lunar Prospector got us to yeah, the Moon has a lot of really interesting chemistry for why we should go back. Then we went another span of several years without visiting the Moon until the European Space Agency went back with Smart-1.
Fraser: This is the coolest mission ever.
Pamela: [Laughter] Why do you say it is the coolest mission ever?
Fraser: Because the way they used to get to the Moon is that they used an Ion Drive. We’ve talked about this in the past. This is where instead of having a chemical rocket where you shoot it out really fast – you turn on this Ion engine which accelerates with electricity – Ions out the back of the Spacecraft.
You don’t need to carry very much fuel so you can launch with a very low Mass. It’s fairly inexpensive. It doesn’t let you go very quickly – accelerate very quickly – but over very long periods of time you can accelerate.
What they did with Smart-1 is they turned on this engine and increased the size of the orbit around the Earth slowly. It just kept getting bigger and bigger elliptical circles around the Earth for like the better part of a month [Laughter] until the ellipse was so big that it included the Moon.
Then they just turned it the other way and slowly brought the orbit back down until it was only orbiting around the Moon. So while normally a Spacecraft just takes from the Earth to the Moon it does it in 2 days, Smart-1 took the better part of a month to make its journey from the Earth to the Moon.
But it did it at a fraction of the cost that any other Spacecraft would do which I though was just wonderful.
Pamela: And what was amazing was just how tiny this little mission was. It had a mass of just 367 kilograms – about 800 pounds. A hundred kilograms of that was propellant related they were using Xenon. But still we’re looking at like a 600 pound (once you get rid of the propellant) Spacecraft that’s tiny. We have like random laboratory equipment hanging around here that is way, way bigger than that.
Here again we’re looking at detecting stuff in a lot of different ways. There was a standard CCD Imager that looked attandard optical wavelengths of light and took images with about 80 meter resolutions so each pixel in the image is about 80 meters across.
They were doing x-ray spectroscopy trying to study the chemicals. They were also using an x-ray Solar monitor to just keep track of what the Sun was up to because depending upon what radiation from the Sun is hitting the Moon, you’re going to get different data.
Lots of really good science including the discovery of Calcium came out of this mission. So Smart-1 again, following up on Prospector we’re starting to now study the chemistry of the Moon.
That was back in 2003 and then we had another gap, four years this time from 2004-2007 happened and then everything started happening all at once last year. We had…
Fraser: This is about the coolest time of Lunar exploration I think – apart from some of the early discoveries.
Pamela: It was like we suddenly re-discovered there was a rock nearby that we could go land on. So then just one after another we start seeing all these missions.
There was the Kengoya or Selene missions launched out of Japan. Japan returned. They have a high-definition camera on their mission. It’s producing some of THE coolest videos ever.
Fraser: They did a re-creation of the Earth rise images. They did it like a movie though. It’s just beautiful and if you just want amazing pictures of the Earth and the Moon these are some of the most beautiful ones ever done.
Pamela: They’re all designed for today’s High-Definition television set so go buy your wonderful high quality Japanese TV and watch your wonderful high quality Japanese Lunar videos – it’s a great combination.
Fraser: But not just Japan, China is there.
Pamela: China is there as well with Chang’e 1 which had the result last week I believe, that no we can’t find visually the water ice on the Moon which is kind of frustrating.
And then just 2 or 3 weeks ago, another mission took off. In this case from India. The Chandrayaan-1 took off October 22 and is off imaging more chemistry experiments.
Then we’re looking in 2009 here in the United States to launch the Lunar Reconnaissance Orbiter and LCROSS which is going to careen itself into the Moon and then into the Moon again.
Fraser: Oh, oh, we’re out of time. That’s what we want to talk about next week [Laughter] which was the future of Lunar exploration including the plans to send humans back to the Moon. So save that part.