The collision between "Proto-Earth" and Theia, from which the Earth and Moon were created 4,500-4,400 million years ago. Both planets had a massive iron core when they collided and created the Moon and Earth.
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The Earth and Moon were created as the result of a giant collision between two planets the size of Mars and Venus. Until now it was thought to have happened when the solar system was 30 million years old or approximately 4.5 billion years ago. But new research shows that the Earth and Moon may have formed much later – perhaps up to 150 million years after the formation of the solar system.
“We have determined the ages of the Earth and the Moon using tungsten isotopes, which can reveal whether the iron cores and their stone surfaces have been mixed together during the collision,” said Tais W. Dahl, from the Niels Bohr Institute at the University of Copenhagen in collaboration with professor David J. Stevenson from the California Institute of Technology (Caltech).
The planets in the solar system were created by collisions between planetary embryos orbiting the newborn sun. In the collisions the small planets congealed together and formed larger and larger planets. When the gigantic collision occurred that ultimately formed the Earth and Moon, it happened at a time when both planetary bodies had a core of metal (iron) and a surrounding mantle of silicates (rock). But when did it happen and how did it happen? The collision took place in less than 24 hours and the temperature of the Earth was so high (7000º C), that both rock and metal must have melted in the turbulent collision. But were the stone mass and iron mass also mixed together?
The age of the Earth and Moon can be dated by examining the presence of certain elements in the Earth’s mantle. Hafnium-182 is a radioactive substance, which decays and is converted into the isotope tungsten-182. The two elements have markedly different chemical properties and while the tungsten isotopes prefer to bond with metal, hafnium prefers to bond to silicates, i.e. rock.
It takes 50-60 million years for all hafnium to decay and be converted into tungsten, and during the Moon forming collision nearly all the metal sank into the Earth’s core. But did all the tungsten go into the core?
“We have studied to what degree metal and rock mix together during the planet forming collisions. Using dynamic model calculations of the turbulent mixing of the liquid rock and iron masses we have found that tungsten isotopes from the Earth’s early formation remain in the rocky mantle,” said Tahl.
The new studies imply that the moon forming collision occurred after all of the hafnium had decayed completely into tungsten.
“Our results show that metal core and rock are unable to emulsify in these collisions between planets that are greater than 10 kilometers in diameter and therefore that most of the Earth’s iron core (80-99 %) did not remove tungsten from the rocky material in the mantle during formation” said Dahl.
The result of the research means that collision that created the Earth and the Moon may have occurred as much as 150 million years after the formation of the solar system, much later than the 30 million years that was previously thought.
Concept drawing of a robotic lunar base. Credit: JAXA
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These ARE the droids we’ve been looking for. The Japanese space agency, JAXA, has plans to build a base on the Moon by 2020. Not for humans, but for robots, and built by robots, too. A panel authorized by Japan’s prime minister has drawn up preliminary plans of how humanoid and rover robots will begin surveying the moon by 2015, and then begin construction of a base near the south pole of the moon. The robots and the base will run on solar power, with total costs about $2.2 billion USD, according to the panel chaired by Waseda University President Katsuhiko Shirai.
Moon base robot. Credit: JAXA
Some of the planned droids weigh about 300 kg (660 pounds) and move on tank-like treads. Reportedly, they will be able to operate within a 100 km (60 mile) radius of the base. They’ll be equipped with solar panels, seismographs to investigate the moon’s inner structure, high-def cameras, and arms to gather rock samples, which will be returned to Earth via a sample return rocket.
The exact location for the base will be chosen from high-resolution images returned by Japan’s Kaguya orbiter, which has provided stunning images of the Moon’s surface.
Previously, JAXA had set a goal of constructing a manned lunar base starting in about 2030, and apparently, the robotic base would be a precursor. That plan calls for astronauts to visit the Moon by around 2020 which is about the same timetable as the Indian Space Research Organization (ISRO) is hoping to have a manned mission to the Moon. The China National Space Administration (CNSA) has said they would like to have a manned lunar mission in 2030. NASA? Not sure yet. The Constellation program to return to the Moon has seemingly been axed, but it’s not going down without a fight from members of Congress and others. But surely, even if NASA decides an asteroid or Mars is their destination of choice, they would have to start by practicing on the Moon.
Let’s all work together on this and perhaps returning to the Moon will actually happen.
Have you ever wanted to explore the Moon? Well, now you can as a virtual astronaut, and you can help lunar scientists answer important questions, as well. New from the Zooniverse — from the same folks that brought you Galaxy Zoo — is Moon Zoo. “We’re asking citizen scientists to help answer different aspects of lunar science and outstanding questions that we still have,” said Dr. Katherine Joy from the Lunar and Planetary Institute and a Moon Zoo science team member.
Moon Zoo uses about 70,000 high resolution images gathered by the NASA’s newest lunar spacecraft. the Lunar Reconnaissance Orbiter. In these images are details as small as 50 centimeters (20 inches) across, and ‘Zooites’ are will be asked to catergorize craters, boulders and more, including lava channels and even all sorts of different spacecraft sitting on the Moon’s surface.
How fun is this latest Zoo project?
“Actually, I have to say after a few days of playing with it I find it much more addictive than the others,” said Chris Lintott, head “zookeeper” of the Zooniverse and chair of the Citizen Science Alliance. “Galaxy Zoo was bad enough but I’m obsessed with the Moon now. I can’t quite believe the variety of the places we’re seeing. People think the Moon is this boring place – they say, ‘we know what it looks like, it’s just grey and flat, right?’ But actually it has its own landscape that is really quite dramatic, especially when the sun is low, so it’s a world well worth exploring.”
Want to join in? Go to the Moon Zoo website, and if you’ve participated any of the previous Galaxy Zoo or Solar Storm Watch projects, you can use the same username and password. If not, it’s easy to sign up.
Under the “How to Take Part” tab you’ll find a tutorial that will teach you how to participate in Moon Zoo.
The two main biggest tasks right now are the Crater Survey, where you can mark all the craters (down to a certain size), and Boulder Wars, where you are shown two images and you determine which has the most boulders.
But Dr. Joy said there will soon be some additional tasks, created from a wish list from lunar scientists. “One of the main tasks we really want to do is to compare these new LRO images to older Apollo panoramic camera images that were taken 40 years ago,” she said. “And what we can do is match these older images against the new images with similar lighting conditions and similar angles at which the camera was pointed at the surface and what we might be able to do is to spot differences that have occurred between 40 years ago and now, which could be in the form of say, new impact craters that have formed from incoming bolides. We might be able to spot new debris flows and landslides that have happened in the past 40 years. This can provide us information about the really recent history of the Moon.”
Questions? There’s a FAQ section and a discussion forum where you can pose queries or discuss any issues or interesting finds with other Zooites.
“We’re hoping to reach out to people that have never really looked at the Moon before in any kind of detail and get them excited about all the secrets the Moon still has,” said Dr. Joy “because there are plenty of new things that people have never looked at before.”
Graphic of how the solar wind flows over the Moon. Credit: NLSI
The Moon keeps getting more interesting all the time! But now comes “shocking” news that exploring polar craters could be much harder and more dangerous than originally thought. New research shows that as the solar wind flows over natural obstructions on the moon, such as the rims of craters at the poles, the craters could be charged to hundreds of volts. “In a nutshell, what we’re finding is that the polar craters are very unusual electrical environments, and in particular there can be large surface charging at the bottom of these craters,” said William Farrell from Goddard Space Flight Center, lead author of a new research on the Moon’s environment.
The moon’s orientation to the sun keeps the bottoms of polar craters in permanent shadow, allowing temperatures there to plunge below minus 400 degrees Fahrenheit, cold enough to store volatile material like water for billions of years. And of course, any resources that may lie in those craters are of interest for any future explorers, should astronauts ever return to the Moon.
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“However, our research suggests that, in addition to the wicked cold, explorers and robots at the bottoms of polar lunar craters may have to contend with a complex electrical environment as well, which can affect surface chemistry, static discharge, and dust cling,” said Farrell, who is part of a lunar Dream Team — the Lunar Science Institute’s Dynamic Response of the Environment at the moon (DREAM) project, which is also part of NASA’s Lunar Science Institute.
Solar wind inflow into craters can erode the surface, which affects recently discovered water molecules. Static discharge could short out sensitive equipment, while the sticky and extremely abrasive lunar dust could wear out spacesuits and may be hazardous if tracked inside spacecraft and inhaled over long periods.
The solar wind is a thin gas of electrically charged components of atoms – negatively charged electrons and positively charged ions — that is constantly blowing from the surface of the sun into space. Since the moon is only slightly tilted compared to the sun, the solar wind flows almost horizontally over the lunar surface at the poles and along the region where day transitions to night, called the terminator.
The researchers created computer simulations to discover what happens when the solar wind flows over the rims of polar craters. They discovered that in some ways, the solar wind behaves like wind on Earth — flowing into deep polar valleys and crater floors. Unlike wind on Earth, the dual electron-ion composition of the solar wind may create an unusual electric charge on the side of the mountain or crater wall; that is, on the inside of the rim directly below the solar wind flow.
Since electrons are over 1,000 times lighter than ions, the lighter electrons in the solar wind rush into a lunar crater or valley ahead of the heavy ions, creating a negatively charged region inside the crater. The ions eventually catch up, but rain into the crater at consistently lower concentrations than that of the electrons. This imbalance in the crater makes the inside walls and floor acquire a negative electric charge. The calculations reveal that the electron/ion separation effect is most extreme on a crater’s leeward edge – along the inside crater wall and at the crater floor nearest the solar wind flow. Along this inner edge, the heavy ions have the greatest difficulty getting to the surface. Compared to the electrons, they act like a tractor-trailer struggling to follow a motorcycle; they just can’t make as sharp a turn over the mountain top as the electrons.
“The electrons build up an electron cloud on this leeward edge of the crater wall and floor, which can create an unusually large negative charge of a few hundred Volts relative to the dense solar wind flowing over the top,” said Farrell.
The negative charge along this leeward edge won’t build up indefinitely. Eventually, the attraction between the negatively charged region and positive ions in the solar wind will cause some other unusual electric current to flow. The team believes one possible source for this current could be negatively charged dust that is repelled by the negatively charged surface, gets levitated and flows away from this highly charged region. “The Apollo astronauts in the orbiting Command Module saw faint rays on the lunar horizon during sunrise that might have been scattered light from electrically lofted dust,” said Farrell. “Additionally, the Apollo 17 mission landed at a site similar to a crater environment – the Taurus-Littrow valley. The Lunar Ejecta and Meteorite Experiment left by the Apollo 17 astronauts detected impacts from dust at terminator crossings where the solar wind is nearly-horizontal flowing, similar to the situation over polar craters.”
“This important work by Dr. Farrell and his team is further evidence that our view on the moon has changed dramatically in recent years,” said Gregory Schmidt, deputy director of the NASA Lunar Science Institute at NASA’s Ames Research Center, Moffett Field, Calif. “It has a dynamic and fascinating environment that we are only beginning to understand.”
Next steps for the team include more complex computer models. “We want to develop a fully three-dimensional model to examine the effects of solar wind expansion around the edges of a mountain. We now examine the vertical expansion, but we want to also know what happens horizontally,” said Farrell. As early as 2012, NASA will launch the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission that will orbit the moon and could look for the dust flows predicted by the team’s research.
Apollo 14 landing site in 3-D. Image: LRO, Anaglyph by Nathanial Burton-Bradford. Click for larger version.
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Time to grab your 3-D glasses! Just got a note from Nathanial Burton-Bradford, one of the image editing wizards we have featured here at Universe Today. His latest handiwork is creating some 3-D analglyphs of images from the Lunar Reconnaissance Orbiter, and particularly of the Apollo landing sites. As Nathanial wrote me, “In a word, WOW!” Nathanial’s images make the lunar landers really stand out and stand *up* in the images, and other features such as tracks and experiments left by the Apollo astronauts become more visible as well. See more images below, and click on the images for larger versions, or see Nathanial’s flickr page for lots more!
Apollo 15 landing site in 3-D. Image by LRO, Analglyph by Nathanial Burton Bradford. Click for larger version.
Apollo 11 landing site in 3-D. Image: LRO, Anaglyph by Nathanial Burton-Bradford. Click for larger version.
[/caption]Despite the close proximity between the Earth and the Moon, there’s a big difference between the surface of the Moon and of Earth’s. Much of the difference between the two celestial bodies is caused by the absence of the following attributes on the Moon: an atmosphere, bodies of water, and plate tectonics.
Since the Earth’s Moon doesn’t have a significant atmosphere, nothing can stop even the smallest meteoroids from striking its surface. As a result, the lunar surface is heavily cratered. As a matter of fact, tiny craters are quite common even on lunar rocks. This was observed on the Moon rocks brought home by the Apollo missions.
By contrast, small meteoroids that pass through the Earth’s atmosphere are easily vaporized and hence are not able to form craters on the land below.
The absence of liquid water on its surface has allowed the Moon to preserve much of its ancient geological features. Here on Earth, erosion can alter and cover formations over time. Plate tectonics, which is also absent on the Moon, is another big factor that makes the terrain of the two celestial bodies different.
Here on Earth, plate tectonics cause volcanic activities, earthquakes, and sea floor spreading.
Due to the lack of water and atmosphere, the lunar regolith (also called “lunar soil”) is noticeably dry and devoid of air. It also does not contain anything organic. The regolith comes from meteor impacts that has plagued the Moon since its inception.
Impact crater sizes on the lunar surface range from the tiny holes that mark lunar rocks to the really big ones like the South Pole Aitken Basin that has a diameter of approximately 2,500 km. Younger craters are superimposed over older ones. This characteristic is used by scientists to determine the relative ages of impact craters.
Basically, it has been observed that the size of impact craters on the surface of the Moon have decreased over time.
Other prominent geological features found on the surface of the Moon include maria, rilles, domes, wrinkle ridges, and grabens.
The maria, which comprise about one-third of the Moon’s near side, are made up of flows of basaltic lava formed from volcanic activities that occurred in the younger years of the Moon. They were once mistaken for seas on the surface of the Moon, hence the name. Maria is the Latin word for seas. The near side refers to the side of the Moon that is constantly facing Earth.
ISS transit of the Moon. Image Credit: Photo courtesy of Fernando Echeverria
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The NASA Image of the Day is a webpage that everyone should visit everyday, as there are always great images of our explorations of space and Earth. But this one has a wow factor that is off the charts. It was taken just minutes before space shuttle Discovery launched this past Monday on April 5, 2010, as the International Space Station flew across the face of the moon over Kennedy Space Center in Florida. I know people who were there who thought it was an poignant event, but here photographer Fernando Echeverria captures the event at just the right milimoment as the ISS reached the dark area on the Moon. Amazing, and such incredible detail, too! Click the image or this link to go to the NASA Image of the Day site where you can find larger versions — suitable for framing or desktops!
The debate on why humans should or should not return to the Moon has been ongoing for years. Two weeks ago, I had the opportunity to hear astronautRon Garan speak eloquently on a subject he is passionate about, water sustainability on planet Earth. Subsequently, I read an essay Garan wrote about the importance of returning to the Moon. Although Garan originally wrote this essay before the cancellation of the Constellation program was announced, he has amended his thoughts to reflect the likelihood that the US won’t be returning to the Moon anytime soon. With Garan’s permission, we are re-publishing his essay in its entirety.
The Importance of Returning to the Moon
(The 8th Continent)
By Ron Garan
NASA Astronaut
On May 10th, 1869, a golden spike joined two railways at Promontory Point, Utah, and the first transcontinental railroad was completed. On January 14th, 2004, a new vision for our Nation’s space exploration program was announced that committed the United States to a long-term human program to explore the solar system starting with a return to the moon. On February 1st 2010, those plans to return to the moon were put on hold. Although our Nation has decided to postpone a return to the moon it is still important to acknowledge the moon’s relevance to life on Earth.
There is no doubt that the railroad changed the world. It opened up frontiers to discovery, settlement, and commerce. The railroad was the backbone for the industrial revolution that provided the largest increase in life expectancy and improvement in quality of life in history. Just as the industrial revolution brought about unprecedented improvements in quality of life so can a new age of space exploration and development, but this time with a positive impact on the environment. To begin a period of sustainable space exploration, both the public and private sectors of our Nation must seize the opportunity and continue on a path to the moon. Artist impression of humans on the Moon. Credit: NASA
Since the Vision for Space Exploration was announced in 2004, there has been an on-going debate about the importance of taking the next step in space exploration, a return to the moon. The reasons for making this the next step include: fulfilling a compelling human need to explore; gaining a foothold on the moon to prepare for journeys to other worlds; easing the world’s energy problems; protecting the planet from disasters; creating moon-based commercial enterprises that will improve life on Earth, conducting scientific research; inspiring young people toward higher education, and utilizing space resources to help spread prosperity throughout the world.
We should not return to the moon for any one of these reasons, but for all of them and more. By first establishing the basic infrastructure for a transportation system between the Earth and the moon and a sustainable, semi-autonomous, permanent human settlement, we will open the door to significant benefits for all. Of course, any permanent lunar base must be economically and politically sustainable and therefore must provide tangible benefits and a return on investment. Ron Garan ready for an EVA in June 2008. Credit: NASA Exploration: Great nations accomplish extraordinary endeavors that help to maintain their leadership in the world. America’s history is built on a desire to open new frontiers and to seek new discoveries. NASA’s vision for space exploration acknowledges that, “Mankind is drawn to the heavens for the same reason we were once drawn into unknown lands and across the open sea. We choose to explore space because doing so improves our lives and lifts our national spirit.”
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Establishing a lunar infrastructure will challenge us to improve the reliability of space transportation and allow us to demonstrate exploration systems and concepts without leaving the relative safety of near-Earth space. Testing systems and concepts at a location that’s a three-day journey from Earth is a logical step before we make the leap of a six-month journey to Mars. Establishing a permanently occupied lunar base also will open the way to detailed study and use of lunar resources, which likely are significantly more economical than lifting all required exploration resources from the Earth’s surface.
Energy: Today, about 1.6 billion people on the Earth don’t have access to electricity. The World Bank estimates that 1.1 billion people live in extreme poverty which leads to 8 million premature deaths every year. In developed countries, higher quality of life is achieved only through a high rate of energy use. Increased energy supply is needed for economic and social development, improved quality of life, and to grow enough food to provide for the citizens of the developing world.
Unless something is done soon, the world will be faced with a crisis of enormous proportions. The United Nations estimates that world population will be approximately 9.1 billion by 2050 with virtually all growth in the 50 poorest countries. The choices that the global society makes to provide for future energy needs will have a profound effect on humanity and the environment.
The moon can supplement Earth-based renewable energy systems to meet future energy demand. Ample energy from the Sun reaches the moon and is not interrupted by weather, pollution or volcanic ash. Solar energy farms on the moon can “beam” limitless clean energy down to where it is needed on Earth or to satellites for relay to the Earth. There are also other potential sources of energy including platinum for fuel cells and an isotope called helium-3, which could be used in fusion reactors of the future.
Supplying energy from the moon will enable us to help provide the Earth’s energy needs without destroying our environment. Artists impression of an asteroid flying by Earth. Credit: NASA Protect the Planet from Disasters: There is a real risk to the Earth’s inhabitants from asteroid impacts and super-volcano eruptions. If a large object the size of Comet Shoemaker-Levy 9 that recently slammed into Jupiter were to hit the Earth, civilization could be destroyed. Much smaller asteroids could cause tremendous damage and loss of life. The moon is a superb location for early detection systems.
A super-volcano eruption is a geologic event of enormous explosive power to affect the global climate for years. Scientists estimate the last such eruption happened 74,000 years ago, and was 10,000 times more powerful than Mount St. Helens. Tremendous amounts of rock and ash were ejected into the air causing a six year long volcanic winter and a 1,000-year instant Ice Age, massive deforestation, disastrous famine, and near extinction of humankind. Scientists estimate that such a super-eruption will occur about once every 100,000 years.
The systems and technology that will be developed for life and work on the moon can be used to develop habitats and systems that could preserve Earth’s inhabitants in the event of a devastating eruption. These systems will also improve our ability to live in extreme environments and can be used to learn how to overcome limited resources and other environmental issues. Astronaut Ron Garan takes a moment to pose for a picture during training for his April 3-20 stay inside the Aquarius Underwater Laboratory off the coast of Key Largo, Florida. Credit: NASA Moon-Based Commercial Enterprises: When the early pioneers headed west and expanded our Nation, they did not carry everything with them that they would need for their journey. They “lived off the land” and we will also need to use those resources available to us along our journey, starting with the moon.
There are numerous moon-based commercial activities that could significantly offset the cost of a moon base. Just a few of these are lunar refueling or servicing stations for satellites, lunar mining and space tourism. These commercial activities would allow us to return national treasures from space and provide a significant return on our space investment.
Scientific research: The moon offers an incredible opportunity to further human understanding and discovery. Since the moon’s ancient surface is relatively undisturbed, study of its geology can help us better understand the geological history of Earth. Further, the moon’s vacuum environment can’t be duplicated on the Earth or in low-Earth orbit, and could lead to new materials, advanced alloys, medicines and innovative ways to deal with limited resources on Earth. Radio telescopes on the far side of the moon would be shielded from all radio signals (noise pollution) from Earth, allowing tremendous sensitivity increases and telescopes pointed at the Earth could identify and predict weather and climate changes.
If we return to the moon just for science and exploration then activities will be limited by the amount of money our nation is willing to devote. But, if we establish a sustainable, economically viable lunar base then our science and exploration will be limited only by our imagination.
Education: Our children are our best investment for the future, and our space program is a tremendous motivator. Our Nation has seen a steady decline in the number of students studying math and science. The space program can help turn this trend around. I can personally attest to the ability of the space program to encourage students based on the fact that I enrolled in math and science courses and began the pursuit of an engineering degree the day after the first space shuttle mission landed. The creation of a permanent lunar base will inspire millions of young people toward higher education and help maintain our Nation’s technological leadership. Astronaut Ron Garan, STS-124 mission specialist, participates in the mission's first EVA in June 2008. Credit: NASA Resources and Other Benefits: Since we live in a world of finite resources and the global population continues to grow, at some point the human race must utilize resources from space in order to survive. We are already constrained by our limited resources, and the decisions we make today will have a profound affect on the future of humanity.
Using resources and energy from space will enable continued growth and the spread of prosperity to the developing world without destroying our planet. Our minimal investment in space exploration (less than 1 percent of the U.S. budget) reaps tremendous intangible benefits in almost every aspect of society, from technology development to high-tech jobs. When we reach the point of sustainable space operations we will be able to transform the world from a place where nations quarrel over scarce resources to one where the basic needs of all people are met and we unite in the common adventure of exploration. The first step is a sustainable permanent human lunar settlement. Artist concept of the Orion capsule in orbit around the Moon. Credit: NASA
How should we go about this important undertaking? A good analogy to look at is the U.S. railroad system. The greatest obstacle for the first railroad developers was financial risk. Purchasing right of way, paying wages for large workforces and buying materials and equipment were prohibitively expensive. But the federal government stepped in, orchestrating massive land grants and other incentives. Once initial government investment was assured, enterprising developers invested enormous sums to bridge vast valleys and tunnel through enormous mountains.
Today we are faced with similar obstacles in the development and use of space for the benefit of humanity. Potential space developers face enormous up-front costs for high-risk, long-term returns on investment. To capitalize on the tremendous moon-based opportunities, our nation should establish the basic infrastructure for a transportation system between the Earth and the moon and a sustainable human settlement on the moon. Once this initial investment is made, commercial revenue-generating activities can be established. Just as our investment in the railroad, interstate road system, hydro-electric dams and other large federal projects have been paid back many times over by increased productivity and quality of life, so will our investment in lunar infrastructure.
We are poised on the doorstep of an incredible opportunity to benefit all of humanity. We have the technology and the ability to make this a reality — we need only the will to see it through. We need to choose a course toward the utilization of space to increase our available resources, global prosperity, quality of life, technological advancement, and environmental stewardship. Just as we look back and thank those before us for developing things most of us take for granted such as railroads and highways, the generations to come should be able to look back and thank us for committing to sustainable space exploration.
Lunar Landscape. Credit: LROC; Goddard Space Flight Center and U of AZ, 3-D modeling and rendering by Bernhard Braun.
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You may recall Bernhard Braun as the wizard from UnmannedSpaceflight.com who created the amazing 3-D images of the Mars avalanche. Now he’s created incredible planetary landscapes for a different world: the Moon. “Actually, this has been my very first attempt with lunar imagery after my previous work has almost been exclusively devoted to Mars,” Braun said. The special software he developed can create three dimensional images from one 2-dimensional picture, but he says the real stars are the spacecraft that gather the data, the Lunar Reconnaissance Orbiter and the Mars Reconnaissance Orbiter. “It is the unprecedented quality together with the unprecedented availability of the raw data that opens the door for everyone to explore new ideas and processing techniques,” Braun said.
See below for more stunning from-the-surface 3-D looks at the Moon – no special 3-D glasses needed!
Lunar Landscape. Credit: LROC; Goddard Spaceflight Center, U of AZ, 3-d rendering and modeling by Bernhard Braun.
I asked Braun if working with images from the Moon was different than working with Mars images. “Creating the single-image shading-derived DEMs from the Moon imagery is both easier and more difficult at the same time when compared to the same process applied to Mars images,” he said. “It’s easier because the lunar surface does not vary as much in its intrinsic albedo, i.e. the visible brightness variations are almost exclusively caused by variations in surface topography, especially at low illumination angles, which can be exploited by the reconstruction algorithm to derive high precision 3D geometry.”
But the work is more difficult because of the totally black shadows on the Moon due to lack of any atmosphere. “So on the Moon any shadows are virtually featureless areas where the 3-D reconstruction algorithm cannot infer anything about the structure of the invisible shadowed surface,” Braun said. “This is different on Mars, where the shadowed areas are usually lit indirectly by considerable amounts of ambient light scattered by dust particles suspended in the atmosphere. So the 3-D models of the Mars surface can be more complete, showing surface details even in shadowed areas.”
Lunar Landscape. Credit: LROC; Goddard Spaceflight Center, U of AZ, 3-d rendering and modeling by Bernhard Braun.
“All in all it’s a lot of fun to play around with both camera and sun positions until an interesting landscape shot is found,” Braun said. “I would like to add that much of the credit must really go to those true wizards at NASA/JPL for not only making and bringing to orbit these almost unearthly powerful cameras like LROC and HiRISE … but also for sharing the whole image catalog via the internet with everyone in the world!”
Braun said he hopes to tackle 3-D views of the Apollo landing sites — which we cannot wait to see!
Before the invention of the telescope in the early 1600’s, man just knew of the Moon — a round, mysterious astronomical object that people would gaze up to in the night sky. As time progressed however, astronomers discovered that the moon isn’t exactly unique to earthlings, and other planets had their own moons. So exactly what is a moon?
A moon is defined to be a celestial body that makes an orbit around a planet, including the eight major planets, dwarf planets, and minor planets. A moon may also be referred to as a natural satellite, although to differentiate it from other astronomical bodies orbiting another body, e.g. a planet orbiting a star, the term moon is used exclusively to make a reference to a planet’s natural satellite.
The first moons to be discovered outside of the Earth’s moon were the Galilean moons of Jupiter, named after astronomer and discoverer Galileo Galilei. The moons Io, Europa, Ganymede, and Callisto are Jupiter’s largest and only the first four to be revealed, as to date, the planet has 63 moons.
Other than the four Galilean moons, Saturn’s Titan and Neptune’s Triton are two other moons which are comparable in size to the Earth’s Moon. In fact, these seven moons are the largest natural satellites in the solar system, measuring more than 3,000 kilometers in diameter. Only the inner planets Mercury and Venus have no moons.
An interesting fact about some of the solar system’s largest moons that most people may not be aware of is that a few of them are geologically active. While we may not see the Moon spewing lava or displaying any evidence of tectonic activity, Jupiter’s Io and Europa, Saturn’s Titan and Enceladus, and Neptune’s Triton have been found to be volcanically active bodies.
If the moon count had a grand total of just one in the olden times, that number has ballooned to 336 as of July 2009, with 168 moons orbiting the six planets, while the rest are moons of dwarf planets, asteroids moons, and natural satellites of Trans-Neptunian objects.
As more and more discoveries are made however, astronomers may find it more difficult to put a really defining line on what can or what can’t be classified as a moon. For instance, can you consider a 10-inch rock that’s orbiting Jupiter a moon? If yes, then there could be thousands or even millions of moons out there. If not, then where do you draw the line? Obviously, even the size of an “official” moon is still up for debate, so other than the simple definition of it being a natural satellite of a planet, there really is no clear cut answer to the question, “What is a moon?”.
Here in Universe Today, we have a nice collection of articles that explain why the Moon landings could not have been faked. Here are some of them:
Moon Rocks – Discusses how the Moon rocks are one of the most tangible objects that prove the landings took place.
Moon Landing Hoax – An explanation that counters some of the points raised by skeptics
Apollo 11 Hoax – another point for point discussion by Jerry Coffey
TV – Alert: Mythbusters and the Moon Hoax Myth – a teaser for the Mythbusters episode featuring the so-called hoax. You’ll find the comments below that article equally interesting, by the way.
Here’s an article from NASA that debunks the hoax theory using the Moon rock arguments. Another article about Moon rocks from the same site.
Episodes about the moon from Astronomy Cast. Lend us your ears!
