17
April
2007
Teaching resources (UK US) designed specifically for this story at Real Science
The story
Scientists at Washington University, with the help of a keen-eyed student, are paving the way for the Phoenix Mission to make a smooth landing on Mars.
The team has been analysing images of the surface of the red planet. Their aim is to make sure the Phoenix, which is due to launch in August, lands in a rock-free spot on the northern plains of Mars.
The craft has to land in a place that won’t have steep slopes or big rocks, said Raymond Arvidson, professor in arts and sciences, and chair of the Washington University earth and planetary sciences department.
“We’ve been looking for locations big enough and homogeneous enough for a high probability of a successful landing. The issue isn’t slopes. The issue is rocks.”
If the lander came down in a place with rocks as big as itself, the whole craft could tilt or tip over. Another problem is the craft’s solar panels. Big rocks would stop these unfurling. Without solar power, which drives seven Phoenix mission instruments, there isn’t much of a mission.
At the heart of the painstaking task of finding a smooth landing is a 21-year-old student at Washington University. Tabatha Heet began working with Arvidson as a work-study student in 2005. She started counting Martian rocks in October 2006.
“Ray asked if I would count some rocks in the original landing area, and I got started, thinking it was going to be a one-time thing,” said Heet. “But it’s turned into a big project. I’ve counted thousands of rocks now.”
Arvidson and his colleagues had settled on a region called Region B for the future landing. But images from an instrument called HIRISE, a feature of the Mars Reconnaissance Orbiter Mission, made them think again.
“The first images for Region B were scary,” Arvidson said. “There are rocks there bigger than the lander – too many big rocks sitting on craters to fit in a landing site.”
With the help of HIRISE images, they looked elsewhere. Heet produced data on the abundance of rocks at different places on the northern plains. This allowed the mission scientists to “zero in on the safe havens”, Arvidson said.
Heet used a software package called ENVI. This shows images and makes measurements.
“All you have to do is draw a line on the image,” she said. “Then ENVI will tell you how long the line is in meters. I go through the image and pick just a small area, because the HIRISE images are too big for one person to count. I’ll make a little subset and then go count every rock in the subset, just by drawing a line where I see the shadow of the rock.
“It’s very slow and makes your eyes go crazy.”
She counted rocks in little areas of the large images. She then made cumulative frequency plots. These showed the number of rocks bigger than any given diameter.
Heet flew out to the Jet Propulsion Laboratory in February. She received a warm round of applause at her introduction to JPL researchers. They questioned her on her technique and stamina. Later, she met a team of automated rock counters who “aggressively” questioned the way she had been counting rocks.
At the meeting, the automated rock counters calibrated their computed numbers to Heet’s hand counts. They are considered ‘ground truth,’ on which all later data are based. She has since corresponded with the group regularly to help make the automated counts more precise.
The automated rock counters map the shape of the shadows, said Arvidson. “From knowing where the sun is, they can compute the rock height and width.
“But they need very intense validation. Tab was the point contact for all of that. We’ve cross-calibrated against the automated counts, because the hand-derived ones are considered anchors.
A human can do a better job with fewer errors “as long as the person is not fatigued”, he added.
Heet’s work has led to the discovery of several possible landing sites. These have at least ten times fewer rocks than the original Region B. They include one desirable location 50 kilometres wide and 250 meters deep. The scientists call it Green Valley.
As data come in from the actual mission, Heet will be at JPL, gathering and interpreting the data, Arvidson said. Just as former Rhodes scholar Bethany Ehlmann, now pursuing a PhD at Brown University, did for the Mars Exploration Rover.
After all her dedicated, painstaking work, Heet often thinks of the mission and the thrill of the Phoenix launch and landing.
“I will certainly be excited when Phoenix launches. I will also probably feel a little bit of pride knowing that I helped make the launch possible. I suspect I’ll be slightly nervous when Phoenix is landing, wondering if I did something wrong and am going to be responsible for making Phoenix crash in a field of huge boulders. Once the lander is on the surface it will be interesting to find out just how accurate all of our predictions were.
“I’m looking forward to it all.”
Topics for group discussion or pupil presentations
1. Research and present current and past thinking about the chances of finding life on Mars.
2. In groups discuss what effect the discovery of life on other planets would have on how people think about science. Would the subject become more popular? Would religions with their view that humans are special disappear? Would the answers to these two questions be different if the extraterrestrial life we discovered were intelligent beings like us or “just” micro-organisms?
3. There are now scientists called astrobiologists who aim to discover if there is life on other planets, by analysing the light that comes from them. Amazingly they are working towards doing this for planets around other stars, as well as in our own solar system. Separating the light of these “exoplanets” and the light of their star has been compared to separating a candle 1000 kilometres away from a lighthouse beside it. Students should read the interview with Giovanna Tinetti then discuss and explain what an astrobiologist actually does.
Links to free activities, resources and lessons
Phoenix mission homepage. Scheduled for launch in August 2007, the Phoenix Mars Mission is designed to study the history of water and habitability potential in the Martian Arctic’s ice-rich soil.
The Phoenix Classroom. Activities and materials to aid understanding of fundamental concepts in science, technology, engineering and mathematics. Includes programs for teacher and student participation.
Ask the Phoenix Mars Mission team a question.
“Spacecraft visiting Mars have returned intriguing images of the surface of the Red Planet for over forty years. Many of these images suggest liquid water once flowed on the surface of Mars. The online video Mars: The Search for Water, the Search for Life looks at some of these images, compares them to similar features on Earth, and looks at the consequences of finding liquid water on Mars.
Phoenix mission fact sheet.
Introduction to what we know and hope to discover about Mars. Learn about the Red Planet by comparing similarities and differences to Earth.
The Phoenix Student Interns Program is an opportunity for high school teachers and students to become part of the science team for the 2007-2008 Phoenix Mars Lander Mission. Selected teachers and students will work with scientists to prepare for surface operations on Mars, analyse data during the mission, and reach out to other students, teachers, and the public through presentations, articles, and web sites. Apply by April 25, 2007
Learn how to organise data in a cumulative frequency table.
Design, construct and test an original model of a bouncing lander. Hold a classroom contest to see which landers work best to keep the cargo from breaking.
Links to more links
Space games and quizzes.
Daily tip for science class discussions and groupwork
Only exceptional lecturers are capable of holding students’ attention for an entire lecture period. It is even more difficult to provide adequate opportunity for students to critically think through the arguments being developed. Consequently, lectures simply reinforce students’ feelings that the most important step in mastering the material is memorizing a zoo of apparently unrelated examples.
In order to address these misconceptions about learning, we developed a method, Peer Instruction, which involves students in their own learning during lecture and focuses their attention on underlying concepts. Lectures are interspersed with conceptual questions, called ConcepTests, designed to expose common difficulties in understanding the material. The students are given one to two minutes to think about the question and formulate their own answers; they then spend two to three minutes discussing their answers in groups of three to four, attempting to reach consensus on the correct answer. This process forces the students to think through the arguments being developed, and enables them (as well as the instructor) to assess their understanding of the concepts even before they leave the classroom.
From Peer Instruction
Posted: Physics
9
April
2007
Links to free teaching resources for the magnetar story
Teaching resources (UK US) designed specifically for this story at www.realscience.org.uk
Ask an astrophysicist: questions and answers about neutron stars.
How do stars form and evolve?
Star Count is a NASA education activity that “turns students into astronomers and gives teachers the resources to capitalize on the fun”. It challenges students to research answers to the questions: “Do people everywhere see the same number of stars in the night sky? Why or why not?” The activity encourages students to go outside at night and count the stars in the sky.
Background on the end of stars.
All the stars in the universe are nuclear furnaces fueled by fusion, which creates all the naturally occurring elements heavier than hydrogen and helium. This video segment from NOVA illustrates the critical role that stars play in creating the elements.
“There’s one kind of star that I find fascinating, and that’s neutron stars. These are the densest things … in the universe, and they actually do have solid surfaces, but it’s a solid form of a whole different state of matter than we’ve ever encountered …”
In a lucky observation, scientists say they have discovered a neutron star in the act of changing into a rare class of extremely magnetic objects called magnetars. No such event has been witnessed definitively until now. This discovery marks only the tenth confirmed magnetar ever found…
The discovery early this year of the first magnetar – a highly magnetized star – put the spotlight on a small class of stars called Anomalous X-ray Pulsars, or AXPs.
“Twenty years ago today, a new astrophysical mystery came banging on the door. It was a burst of gamma radiation so strong that it swamped detectors. It was the calling card for a new type of star – the magnetar.
Links to more
NASA online resources on stars
Teaching tools and astronomy basics from Amazing Space.
The story:
Cosmic hiccup
Using data from X-ray satellites, astronomers have caught a magnetar in a giant cosmic hiccup.
When it comes to eerie astrophysical effects, magnetars are hard to beat. The massive remains of exploded stars, magnetars are the size of mountains. But they weigh as much as our sun. This makes them incredibly dense.
Magnetars are a type of neutron star. But they possess magnetic fields hundreds of trillions of times as powerful as Earth’s magnetic field – which turns compass needles north.
The giant cosmic hiccup still has scientists puzzled. The researchers describe it in multiple reports in the Astrophysical Journal and Monthly Notices of the Royal Astronomical Society.
The magnetar is in a star cluster about 15 000 light-years away, in the Ara constellation. This is in the southern hemisphere. The magnetar goes by the official name of CXOU J164710.2-455216. Informally it is known as the Westerlund 1 magnetar.
“We only know of about a dozen magnetars,” says Michael Muno. He is a scientist at the California Institute of Technology’s Space Radiation Laboratory. He is the original discoverer of the magnetar.
“In brief, what we observed was a seismic event on the magnetar, which tells us a lot about the stresses these objects endure.”
In September 2005, about a year after Muno found the magnetar, the object produced a burst of radiation. Luckily this came at a time when it was being observed closely by several satellites. These included the European Space Agency’s X-ray satellite, XMM-Newton, and NASA’s Swift X-ray and gamma-ray observatory.
Just five days before the burst, Muno and his collaborators had been looking at the magnetar with XMM-Newton. They saw it in the relatively calm state in which he had first found it.
As most magnetars do, this one produces a beam of X-rays. These sweep across the heavens once every ten seconds. Earth lies in the path of this beam. So the magnetar’s speed of rotation could be determined very precisely.
The event that produced the burst caused the magnetar to shine 100 times more brightly. It created three separate beams that sweep past Earth where only one had existed before. It sped up its rotation rate by about a thousandth of a second.
Muno says more work is needed to understand what happened. The magnetar is built of matter far denser than anything on Earth. Its composition is a bit of a mystery.
But it is possible to make educated guesses. This can be done by extending theories that explain other neutron stars:
The magnetic fields inside the neutron star are probably wound up, like a twisted spring. As the magnetic fields unwind they create stresses in the outer crust, rather like the stresses created by plate tectonics on Earth.
The crust would resist these stresses for a while. But eventually it would fracture. This would produce a seismic event – a “starquake”. The fractures would cause the magnetar’s surface to shine brightly, from many sources.
In addition, there is reason to think that part of the interior of the neutron star is liquid. This may be rotating faster than the crust. The seismic event could cause this fluid to become attached to the crust. That would make the outer crust speed up slightly. “We think the crust cracked,” Muno says.
The observations are important for two reasons, he adds. “First, we have now seen another way in which these exotic objects dissipate their internal fields as they age.
“Second, this event was only spotted because a team of us were concentrating hard on this newly discovered object. The fact that we saw the event only a year after we discovered the magnetar implies that dozens more could be lurking in our Galaxy.
“If we find many more of these magnetars, we will have to re-evaluate our understanding of what happens when stars die,” says Gianluca Israel. He is an Italian astronomer who is publishing a separate paper on the magnetar with his collaborators in the Astrophysical Journal.
Muno is lead author of a paper appearing this week in Monthly Notices of the Royal Astronomical Society.
Posted: Physics
2
April
2007
Links to free teaching resources for the story on electric sails
Teaching resources (UK US) designed specifically for this story at www.realscience.org.uk
The Sun produces a solar wind — a continuous flow of charged particles — that can affect us on Earth. It can disrupt communications, navigation systems and satellites, and cause power outages such as the Canadian blackout in 1989. In this video segment adapted from NASA, learn about solar storms and their effects on Earth.
Centauri Dreams is the place to go for the latest news, made easy to understand, on all aspects of space travel. This latest posting provides more insight than the press release, but teachers should be careful of letting young kids loose on it, because of a little bad language in one of the comments.
An electric sail has not yet been built. But a related method of propulsion powered the NASA mission Deep Space 1, which did fly. “An ion engine is much the same as what you experience when you pull hot socks out of the clothes dryer on a cold winter day. The socks push away from each other because they are electrostatically charged, and like charges repel.”
Gain a feel for the distances involved in space travel by creating scale models.
How do vessel design, navigation, and propulsion affect exploration? This lesson compares vessel design, navigation, and propulsion used by early Jamestown explorers to those used by NASA. Students use maps and coordinate planes to demonstrate the Global Positioning System and to compare 17th-century mapmaking to modern technology. They conduct experiments about sails and other propulsion systems.
Latest news on solar sails.
Background and animation on the electric sail.
Links to more
The new electric sail research paper.
The story:
Electric sail
Space travel is difficult for two main reasons: Very high speeds are needed to get anywhere at all, because space is enormous. And high speeds usually mean high energy and high costs.
But some sources of energy come free or at least very cheap. One of these is solar sails, which use the feather-touch of sunshine on vast sheets of fabric to shift a spaceship.
Another idea is to harness the energy in the solar wind, through its effect on electrically charged wires. This electric sail concept has now been studied in detail by scientists in Finland. Their work has just been published in Annales Geophysicae.
The solar wind consists of high-energy, charged particles thrown out by the sun. These travel across space at speeds from 300-800 kilometres per second. On Earth they power the aurorae, the stunning displays of light in the sky, which have many other names such as the “northern lights”.
On average the pressure of the solar wind is 2 nano-pascal, which is just a fifth of a gram weight on each square kilometre. (One gram is the weight of a paperclip.)
To use such a weak pressure to propel a spacecraft you need a very large area of sail. Larger than a solid surface can provide. So the electric sail uses the idea of forming an electric field around a thin, charged wire.
This wire is kept at high voltage by a solar-powered electron gun on board the spacecraft. A 20-km long tether, made of wire thinner than human hair, can fit into a small reel. But it provides a square kilometre of effective area when stretched out in space and charged up.
In the Annales Geophysicae paper the scientist describe 2-dimensional simulations they ran on a supercomputer. These calculated the thrust per meter of tether length. Different solar wind conditions and tether voltages were studied. The aim was to test if the whole approach could work.
Theoretical analysis and one-dimensional simulations were used to validate the results.
These show that around 50 nano-newtons force per meter of wire can be achieved in a normal solar wind.
This could accelerate a light spacecraft up to final speeds in the range 50-100 kilometres per second. This is 10 to 20 astronomical units (1AU) a year. One AU is the distance from earth to the sun.
At such high speeds a craft powered by the electric sail could reach Pluto in less than four years. It could fly out of the heliosphere into interstellar space in less than 15 years.
The electric sail needs no propellant or other consumables. So one of the possible applications is cheap transportation of raw materials. These include water mined from asteroids and used to make fuel for other spaceships.
Posted: Physics
24
March
2007
Links to free teaching resources for the story on Saturn’s moon Enceladus:
Teaching resources (UK US) designed specifically for this story at www.realscience.org.uk
Story, audio files, images and podcast from NASA.
Saturn’s tiny moon Enceladus is a “highlight of the Cassini mission and should be targeted in future searches for life.”
Centauri Dreams, one of my favourite blogs, on the topic of little Enceladus. The blog is about the science of star-travelling: “Building a star-faring craft is something like building a cathedral: it will take the combined efforts of scientists and engineers through several generations to make it happen.”
Where is Cassini now?
Make your own Cassini presentation.
Download lesson sets for Reading, Writing and Rings, the Cassini Mission’s language arts and science program for students in grades 1-4.
Without liquid water, terrestrial life could not exist. All living organisms on Earth depend on water and its unique chemical and physical properties. In the search for life beyond Earth, scientists have focused their efforts on looking for signs of liquid water. This essay from NOVA Online explores why liquid water is considered an essential ingredient for life as we know it
Imaginative captain’s log and wonderful images from Cassini
Voyage to the mystery moon. From Nova.
Background on how long is a day on Saturn. Useful for the science methods, but the conclusion is now superseded by this latest story.
More links
NASA resources and information on Enceladus.
NASA image set
Nice explanation of difference between rotation period and length of day. Note that Saturn’s figures are wrong.
Fast facts on Saturn.
The story:
All in a day’s work
How long is a day? Well it depends on where you’re standing. One day is the time it takes for the sun to rotate right around the sky, and come back to the same place. Of course it’s the planet spinning that makes the sun seem to move.
Because planets spin at different rates, each has a different length of day. You might think these numbers would be well known, but not all of them are. Rocky planets are easy. Scientists simply choose a landmark on the surface and wait till it comes round again.
But four planets are made of gas not rock. So finding fixed features on Jupiter, Saturn, Uranus and Neptune is tricky.
Until now a method of measuring radio waves from deep inside these gas giants was thought to be accurate. These radio waves are linked to the planet’s magnetic field. This should rotate at the same rate as the planet.
New data from NASA’s Cassini spacecraft show that things are more complicated at Saturn. The problems are being caused by a small moon called Enceladus. At just over 300 miles in diameter this satellite of Saturn could easily fit into Arizona. It’s a small moon. But it is giving scientists a big headache.
The new data from Cassini show how Enceladus is making it almost impossible to measure the length of Saturn’s day. They demonstrate that the planet’s magnetic field is rotating at a different rate to the planet.
The reason seems to be electrically charged particles coming from huge geysers on Enceladus. These are spewing water vapour and ice.
These results are based on joint observations by two Cassini instruments, the radio and plasma wave instrument and the magnetometer. The new findings are reported online in the 22 March issue of Science
No one could have predicted that Enceladus would have such an effect on the radio technique used to measure the length of Saturn’s day, said Dr. Don Gurnett of the University of Iowa.
Gurnett is the principal investigator on the radio and plasma wave science experiment onboard NASA’s Cassini spacecraft.
What seems to be happening is this. Neutral gas particles are thrown out by geysers on Enceladus. They form a donut-shaped ring around Saturn. As these particles become electrically charged, they are captured by Saturn’s magnetic field. They then form a disk of ionised gas or plasma. This surrounds the planet near the equator.
The scientists now believe that the period Cassini has been measuring from radio emissions is not the length of the Saturn day. Instead it is the rotation of this plasma disk. At present Saturn’s cloud motion means that no technique is known that can accurately measure the planet’s internal rotation.
“We have linked the pulsing radio signal to a rotating magnetic signal,” said Dr. David Southwood, director of science at the European Space Agency. “Once each rotation of Saturn’s magnetic field, an asymmetry in the field triggers a burst of radio waves. We have then linked both signals to material that has come from Enceladus.
The direct link between radio, magnetic field and deep planetary rotation has been taken for granted, said Michele Dougherty of Imperial College London. He is principal investigator on Cassini’s magnetometer instrument.
“Saturn is showing we need to think further.”
Posted: Physics
11
March
2007
Links to free activities, resources and lesson plans
Teaching resources (UK US) designed specifically for this story at www.realscience.org.uk
“For the very first time, astronomers have witnessed the speeding up of an asteroid’s rotation, and have shown that it is due to a theoretical effect predicted but never seen before.” News release, photos and movies from European Space Observatory.
Online video, teachers’ notes and pupil interactives on near-Earth asteroids.
Earth impact effects program: Provides an easy way to calculate the environmental effects of an asteroid strike on Earth. “Plug in a few size and impact parameters, and find the total damage inflicted with the click of a button.” From University of Arizona.
Interactive lessons and virtual labs on asteroid formation, the physics of asteroid trajectories, etc. “Teachers can also download fun problem-solving activities for use in the classroom.”
Newton’s 3rd Law illustrated through astronauts working working in space. “This video segment, adapted from NOVA, illustrates the significance of Newton’s law to space-walking astronauts and the engineers who design their spacecrafts.”
“Explore the planets, comets and asteroids on an interactive virtual fly-through. Zoom in close on a particular planet or choose a different orbit view to see the whole system from afar. The data sheets let you discover more about some of the elements that make up our Solar System.”
“The University of Pisa offers a comprehensive monthly catalog of known asteroids and other large orbital objects, as well as links to several major observatories.” Enter 2000 PH5 in the search engine to find more facts about the little asteroid than you thought possible.
NASA’s Near Earth Object Program detects, tracks and analyzes large asteroids and comets that might be on a collision course with Earth. Find recent close approaches, view asteroid orbit diagrams, see impact risk assessments. Includes multimedia introduction.
The Asteroid Club encourages amateurs to learn to identify and observe asteroids. “While the deep sky objects observable by amateurs remain the same, year after year, the asteroids are constantly moving against the background of the constellations. By learning to identify asteroids you will greatly enhance your observing skills.”
Background on the YORP effect.
“In 1873, while investigating infrared radiation and the element thallium, the eminent Victorian experimenter Sir William Crookes developed a special kind of radiometer, an instrument for measuring radiant energy of heat and light.”
Posted: Physics
1
March
2007
Links to free activities, resources and lesson plans
Teaching resources (UK US) designed specifically for this story at www.realscience.org.uk
“When Gordon Moore began working at Shockley Semiconductor in 1956, he barely knew what a semiconductor was. Within ten years he was well on his way to being one of the greatest visionaries of the semiconductor world.” Includes audio of Moore talking about the impact of the transistor.
“The Transistor was probably the most important invention of the 20th Century, and the story behind the invention is one of clashing egos and top secret research.” Portal to lots of good stuff for teachers and pupils. For example:
“To help students better understand the transistor and its impact on technology, the documentary and website are accompanied by this Teachers’ Guide… The Teachers’ Guide includes a range of activities, appropriate for middle-school or high-school use, plus a series of profiles of young scientists and their work.
All about Moore’s Law. From Intel.
“This interactive activity from NOVA describes the crystalline structure of metal and uses animations to illustrate the molecular changes that occur when a metallic substance is bent, heated, or otherwise changed by external forces.”
“Einstein’s relativity theory proven with the ‘lead’ of a pencil.” Earlier press release about graphene.
“Researchers have discovered the world’s first single-atom-thick fabric, which reveals the existence of a new class of materials and may lead to computers made from a single molecule.” Original discovery of graphene.
“Graphite, the material that gives pencils their marking ability, could be the basis for a new class of nanometer-scale electronic devices that have the attractive properties of carbon nanotubes – but could be produced using established microelectronics manufacturing techniques.”
“Graphene is a single layer of carbon atoms densely packed in a honeycomb crystal lattice. The material is made from splitting graphite apart into individual atomic planes, through a process similar to tracing with a pencil. The resulting atomic sheet is unexpectedly stable, highly flexible and strong, and very conductive.” Earlier press release about Graphene.
“The structure of a material may be divided into four levels: atomic structure, atomic arrangement, microstructure, and macrostructure.” Page on crystal structures with nice pics and links.
“Materials science and engineering : ‘never heard of it’ is a common enough response both from students at school as well as from the general public. Compared to other science and engineering subjects, it can be a bit of a mystery… However, it is a vitally important subject, underlying all the others and playing a key role in developments in science and technology… most major technological advances throughout history have only been possible through a better understanding and use of materials.”
Links to more links
Transistorized!
Animation gallery of nanotubes, fullerenes etc.
Posted: Physics
14
February
2007
Scientists have produced the first hiker’s maps of Mars. These give detailed height contours and names of geological features … more
Links to free activities, resources and lessons
Teaching resources (UK US) prepared specifically for this story from www.realscience.org.uk.
Mars Express homepage, with videos from the HRSC, as well as animations and screensavers.
Lesson on getting around on the surface of Mars. Students design a surface-exploration vehicle. From Discovery School.
Interactive maps, reports and presentations about landing sites on Mars. Includes visible light images, thermal images, topography, geology. From NASA.
Students research the types of technology used to map and explore Mars. They imagine they’re working as technology experts for NASA, and create visual presentations to show the American public the types of technology that their tax dollars are funding for Mars mapping and exploration. From National Geographic.
Introduces students to common map projections and representations, and asks them to consider how each can be used to show specific features of Mars. Students draw three different representations of Mars, and illustrate each with details of research they have conducted on the planet.
Seven lessons designed to educate students on the exploration of Mars. Includes topographic and geologic mapping, Martian volcanoes and geology, and image interpretation. Lessons include hands-on activities, maps and overheads and links to additional resources.
Online tutorial designed to assist geoscience educators in effective teaching using spatial representations, including maps, cross sections and 3-D models. The tutorial draws upon cognitive science research
The Mars Exploration Rovers have exceeded expectations in digging up geological clues they have dug up about the planet’s past. In this interactive tour from NOVA Online, the mission’s principal science investigator, Steve Squyres, describes some of the great discoveries made by Spirit and Opportunity. From Teachers’ Domain. Simple registration required.
High-resolution images taken from low orbit provide evidence of the impact of wind and water erosion on the Martian surface. A photographic database of NASA images illustrating the forces of erosion that have reshaped much of the surface of the Red Planet.
Links to more
More information on the new maps, with some samples.
More stories and resources at www.realscience.org.uk
Posted: Physics
