A 20-km asteroid has just been predicted to hit Earth and you want to know if a. You should run for it, b. You should call Bruce Willis, or c. You can rest easy because your part of the world won’t be affected. All you have to do is input the parameters of the asteroid on the recently updated “Impact Earth” website, and you’ll find out everything about what an impactor will do to Earth, including an estimate of the size of the crater, how far away you’ll need to be in order to avoid being affected by the impact (and if that is possible), tsunami wave height, and other details of the subsequent disaster. The fun part is, you can simulate the destruction of Earth multiple times, without hurting anyone.
The original Impact Earth website was created in 2002 for use by NASA and homeland security. The new version, built in a collaboration between Purdue University and Imperial College London, is more user-friendly for the general public, as well as providing more visual details of an impact. Besides being rather fun to play around with, the website is highly educational about what a various sized impacts would do Earth, depending on if it hit ground or water.
Fire scars in Australia are featured in this image photographed by an Expedition 5 crewmember on the International Space Station (ISS). Bright orange fire scars show up the underlying dune sand in the Simpson Desert, Credit: NASA
The International Space Station has been orbiting the Earth every day for over 10 years, and the astronauts all say their favorite pastime is looking at the Earth. During the past 10 years, the crews have taken some great pictures of our planet, and these images provide a unique look at our world. These are just a few of the spectacular views of Earth from the space station.
In another case of NASA reusing and recycling spacecraft, two of the five THEMIS spacecraft — which were studying the cause of geomagnetic substorms here on Earth — have a new mission. They made some very unique and complex maneuvers to reach two different LaGrange Points, and will turn their focus on the Moon. Particularly, they will try to determine how the solar wind electrifies, alters and erodes the lunar surface. This is timely since the discovery last year of water across the surface of the Moon which may be created by the solar wind interacting with the lunar surface.
The original THEMIS mission (Time History of Events and Macroscale Interactions during Substorms) featured five satellites that have now successfully completed their 2 year mission. Because they are continuing to work perfectly, NASA is re-directing the outermost two spacecraft to special orbits at and around the Moon. This new mission, which is called ARTEMIS: Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun.
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It took more than a year and nearly all remaining fuel aboard the satellites to get them to the L1 and L2 Lagrangian points, where one is located on the far side of the Moon, and the other on the Earth-facing side. ARTEMIS-P1 is the first spacecraft to navigate to and perform stationkeeping operations around the Earth-Moon L1 and L2 Lagrangian points.
On August 25, 2010, ARTEMIS-P1 reached the L2 Lagrange point on the far side of the Moon. Following close behind, ARTEMIS-P2 entered the opposite L1 Lagrange point on Oct. 22nd.
As the Moon orbits the Earth, it passes in and out of the Earth’s magnetic field and the million-mile per hour stream of solar wind particles. While in these regions, the two ARTEMIS spacecraft will seek evidence for turbulence, particle acceleration, and magnetic reconnection, three fundamental phenomena that control the nature of the solar wind’s interaction with the Earth’s magnetosphere.
By using their instruments and unique two-point vantage points, the spacecraft will study the vacuum the Moon carves out in the solar wind, and the processes that eventually fill this lunar wake. Nearer the Moon, they will observe the effects of surface electric fields, ions sputtered off the lunar surface, and determine the internal structure of the Moon from transient variations in its magnetic field induced by external changes.
Apollo 9 astronaut Rusty Schweickart is among an international group of people championing the need for the human race to prepare for what will certainly happen one day: an asteroid threat to Earth. In an article on Universe Today published yesterday, Schweickart said the technology is available today to send a mission to an asteroid in an attempt to move it, or change its orbit so that an asteroid that threatens to hit Earth will pass by harmlessly. What would such a mission entail?
In a phone interview, Schweickart described two types of “deflection campaigns” for a threatening asteroid: a kinetic impact would roughly “push” the asteroid into a different orbit, and a gravity tractor would “tug slowly” on the asteroid to precisely “trim” the resultant change course by using nothing more than the gravitational attraction between the two bodies. Together these two methods comprise a deflection campaign.
Artist Impression of Deep Impact - Credit: NASA
“In a way, the kinetic impact was demonstrated by the Deep Impact mission back in 2005,” said Schweickart. “But that was a very big target and a small impactor that had relatively no effect on the comet. So, we haven’t really demonstrated the capability to have the guidance necessary to deflect a moderately sized asteroid.”
Most important, the gravity tractor spacecraft would arrive prior to the kinetic impactor, precisely determine the asteroid’s orbit and observe the kinetic impact to determine its effectiveness. Following the kinetic impact it would then determine whether or not any adjustment trim were required.
“You want to know what happens when you do a kinetic impact, so you want an ‘observer’ spacecraft up there as well,” Schweickart explained. “You don’t do a kinetic impact without an observation, because the impactor destroys itself in the process and without the observer you wouldn’t know what happened except by tracking the object over time, which is not the best way to find out whether you got the job done.”
So, 10-15 years ahead of an impact threat — or 50 years if you have that much time — an observer spacecraft is sent up. “This, in fact, would also be a gravity tractor,” Schweickart said. “It doesn’t have to be real big, but bigger gets the job done a little faster. The feature you are interested in the outset is not the gravity tractor but the transponder that flies in formation with the asteroid and you track the NEO, and back on Earth we can know exactly where it is.”
Schweickart said even from ground tracking, we couldn’t get as precise an orbit determination of an NEO as we could by sending a spacecraft to the object. Additionally, generally speaking, we may not know when we send an observer spacecraft what action will be required; whether an impact will be required or if we could rely on the gravity tractor. “You may launch at the latest possible time, but at that time the probability of impact may be 1 in 5 or 1 or 2,” Schweickart said. “So the first thing you are going to do with the observer spacecraft is make a precise orbit determination and now you’re going to know if it really will impact Earth and even perhaps where it will impact.”
Artist concept of an impactor heading towards an asteroid. Credit: ESA
After the precise orbit is known, the required action would be determined. “So now, if needed you launch a kinetic impactor and now you know what job has to be done,” Schweickart said. “As the impactor is getting ready to impact the asteroid, the observer spacecraft pulls back and images what is going on so you can confirm the impact was solid, –not a glancing blow — and then after impact is done, the observer spacecraft goes back in and makes another precision orbit determination so that you can confirm that you changed its velocity so that it no longer will hit the Earth.”
The second issue is, even if the NEO’s orbit has been changed so that it won’t hit Earth this time around, there’s the possibility that during its near miss it might go through what is called a “keyhole,” whereby Earth’s gravity would affect it just enough that it would make an impact during a subsequent encounter with Earth. This is a concern with the asteroid Apophis, which is projected to miss Earth in 2029, but depending on several factors, could pass through a keyhole causing it to return to hit Earth in 2036.
“So if it does go through that keyhole,” said Schweickart, “now you can use the gravity tractor capability of the spacecraft to make a small adjustment so that it goes between keyholes on that close approach. And now you have a complete verified deflection campaign.”
Schweickart said a Delta-sized rocket would be able to get a spacecraft to meet up with an asteroid. “A Delta rocket would work,” he said, “but if there is a more challenging orbit we might have to use something bigger, or we may have to use a gravity assist and do mission planning for type of thing which hasn’t been done yet. So we can get there, we can do it – but ultimately we will probably need a heavy lift vehicle.”
As for the spacecraft, we can use a design similar to vehicles that have already been sent into space.
“A gravity tractor could be like Deep Space 1 that launched in 1998,” Schweickart said. “ You can make any spacecraft into a gravity tractor fairly easily.”
Rusty Schweickart
But it hasn’t been demonstrated and Schweickart says we need to do so.
“We need to demonstrate it because we – NASA, the technical community, the international community — need to learn what you find out when you do something for the first time,” he said. “Playing a concerto in front of an audience is quite different from playing it alone in your house.”
A new NASA image of Earth, by Robert Simmon and Marit Jentoft-Nilsen, based on MODIS data.
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Despite recent news of potential habitable exoplanets and amazing images of Mars and the Saturn system returned from visiting spacecraft, the ol’ home planet is still about the most gorgeous-looking planetary body out there. We first saw it as a whole “blue marble” when the Apollo astronauts sent back pictures while circling the Moon, and it has been said that the original “Blue Marble” image taken by the Apollo 17 crew has been one of the most viewed and most influential images ever. But truth be told, that “Blue Marble” really wasn’t all that blue (see the original below). However, this new look at the home world shows how prevalent water really is. This composite image is based largely on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.
It sure is pretty.
According to the NASA Earth Observatory website, Earth’s water content is about 1.39 billion cubic kilometers (331 million cubic miles), with the bulk of it, about 96.5%, being in the global oceans. As for the rest, approximately 1.7% is stored in the polar icecaps, glaciers, and permanent snow, and another 1.7% is stored in groundwater, lakes, rivers, streams, and soil. Only a thousandth of 1% of the water on Earth exists as water vapor in the atmosphere.
Here’s the original “Blue Marble,” the view of the Earth as seen by the Apollo 17 crew traveling toward the moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is the first time the Apollo trajectory made it possible to photograph the south polar ice cap. Almost the entire coastline of Africa is clearly visible. The Arabian Peninsula can be seen at the northeastern edge of Africa. The large island off the coast of Africa is Madagascar. The Asian mainland is on the horizon toward the northeast.
The original 'Blue Marble' taken by Apollo 17. Credit: NASA
Princeton University has developed software that can produce realistic “movies” of earthquakes based on complex computer simulations, and these visualizations will be available on the internet within hours of a disastrous upheaval. For example, this video of a 5.7 scale Earthquake off the coast of Peru occurred yesterday, September 22, 2010. “In our view, this could truly change seismic science,” said Princeton’s Jeroen Tromp, a professor of geosciences and applied and computational mathematics, who led the effort. “The better we understand what happens during earthquakes, the better prepared we can be. In addition, advances in understanding seismic waves can aid basic science efforts, helping us understand the underlying physics at work in the Earth’s interior. These visualizations, we believe, will add greatly to the research effort.”
An aurora seen over the South Pole, from the ISS. Credit: Doug Wheelock, NASA.
For many people around the world the ability to see the Aurora Borealis or Aurora Australis is a rare treat. Unless you live north of 60° latitude (or south of -60°), or who have made the trip to tip of Chile or the Arctic Circle at least once in their lives, these fantastic light shows are something you’ve likely only read about or seen a video of.
But on occasion, the “northern” and “southern lights” have reached beyond the Arctic and Antarctic Circles and dazzled people with their stunning luminescence. But what exactly are they? To put it simply, auroras are natural light displays that take place in the night sky, particularly in the Polar Regions, and which are the result of interaction in the ionosphere between the sun’s rays and Earth’s magnetic field.
Description:
Basically, solar wind is periodically launched by the sun which contains clouds of plasma, charged particles that include electrons and positive ions. When they reach the Earth, they interact with the Earth’s magnetic field, which excites oxygen and nitrogen in the Earth’s upper atmosphere. During this process, ionized nitrogen atoms regain an electron, and oxygen and nitrogen atoms return from an excited state to ground state.
High-speed particles from the Sun, mostly electrons, strike oxygen and nitrogen atoms in Earth’s upper atmosphere. Credit: NASA
Excitation energy is lost by the emission of a photon of light, or by collision with another atom or molecule. Different gases produce different colors of light – light emissions coming from oxygen atoms as they interact with solar radiation appear green or brownish-red, while the interaction of nitrogen atoms cause light to be emitted that appears blue or red.
This dancing display of colors is what gives the Aurora its renowned beauty and sense of mystery. In northern latitudes, the effect is known as the Aurora Borealis, named after the Roman Goddess of the dawn (Aurora) and the Greek name for the north wind (Boreas). It was the French scientist Pierre Gassendi who gave them this name after first seeing them in 1621.
In the southern latitudes, it is known as Aurora Australis, Australis being the Latin word for “of the south”. Auroras seen near the magnetic pole may be high overhead, but from farther away, they illuminate the northern horizon as a greenish glow or sometimes a faint red. The auroras are usually best seen in the Arctic and Antarctic because that is the location of the poles of the Earth’s magnetic field.
The South Pole Telescope under the aurora australis (southern lights). Credit: Keith Vanderlinde
Names and Cultural Significance:
The northern lights have had a number of names throughout history and a great deal of significance to a number of cultures. The Cree call this phenomenon the “Dance of the Spirits”, believing that the effect signaled the return of their ancestors.
To the Inuit, it was believed that the spirits were those of animals. Some even believed that as the auroras danced closer to those who were watching them, that they would be enveloped and taken away to the heavens. In Europe, in the Middle Ages, the auroras were commonly believed to be a sign from God.
According to the Norwegian chronicle Konungs Skuggsjá (ca. 1230 CE), the first encounter of the norðrljós (Old Norse for “northern light”) amongst the Norsemen came from Vikings returning from Greenland. The chronicler gives three possible explanations for this phenomena, which included the ocean being surrounded by vast fires, that the sun flares reached around the world to its night side, or that the glaciers could store energy so that they eventually glowed a fluorescent color.
Auroras on Other Planets:
However, Earth is not the only planet in the Solar System that experiences this phenomena. They have been spotted on other Solar planets, and are most visible closer to the poles due to the longer periods of darkness and the magnetic field.
Image of Saturn’s aurora taken by the Huddle Space Telescope and seen in ultraviolet wavelengths. Credit: ESA/NASA/Hubble
For example. the Hubble Space Telescope has observed auroras on both Jupiter and Saturn – both of which have magnetic fields much stronger than Earth’s and extensive radiation belts. Uranus and Neptune have also been observed to have auroras which, same as Earth, appear to be powered by solar wind.
Auroras also have been observed on the surfaces of Io, Europa, and Ganymede using the Hubble Space Telescope, not to mention Venus and Mars. Because Venus has no planetary magnetic field, Venusian auroras appear as bright and diffuse patches of varying shape and intensity, sometimes distributed across the full planetary disc.
An aurora was also detected on Mars on August 14th, 2004, by the SPICAM instrument aboard Mars Express. This aurora was located at Terra Cimmeria, in the region of 177° East, 52° South, and was estimated to be quite sizable – 30 km across and 8 km high (18.5 miles across and 5 miles high).
Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their tops, auroras can form. Credit: NASA
Though Mars has little magnetosphere to speak of, scientists determined that the region of the emissions corresponded to an area where the strongest magnetic field is localized on the planet. This they concluded by analyzing a map of crustal magnetic anomalies compiled with data from Mars Global Surveyor.
More recently, an aurora was observed on Mars by the MAVEN mission, which captured images of the event on March 17th, 2015, just a day after an aurora was observed here on Earth. Nicknamed Mars’ “Christmas lights”, they were observed across the planet’s mid-northern latitudes and (owing to the lack of oxygen and nitrogen in Mars’ atmosphere) were likely a faint glow compared to Earth’s more vibrant display.
In short, it seems that auroras are destined to happen wherever solar winds and magnetic fields coincide. But somehow, knowing this does not make them any less impressive, or diminish the power they have to inspire wonder and amazement in all those that behold them.
A powder snow avalanche in the Himalayas near Mount Everest. Credit: Wikipeida Commons/ Ilan Adler
Have you ever noticed how the snow packs on a car windshield after a heavy snowfall? While the temperature is cold, the snow sticks to the surface and doesn’t slide off. After temperatures warm up a little, however, the snow will slide down the front of the windshield, often in small slabs. This is an avalanche on a miniature scale.
On the other hand, a mountain avalanche in North America might release 229,365 cubic meters (300,000 cubic yards) of snow. That’s the equivalent of 20 football fields filled 10 feet deep with snow. However, such large avalanches are often naturally released. They are primarily composed of flowing snow but given their power, they are also capable of carrying rocks, trees, and other forms of debris with them.
In mountainous terrain avalanches are among the most serious objective hazards to life and property, with their destructive capability resulting from their potential to carry an enormous mass of snow rapidly over large distances.
Classification:
Avalanches are classified based on their form and structure, which are also known as “morphological characteristics”. Some of the characteristics include the type of snow involved, the nature of what caused the structural failure, the sliding surface, the propagation mechanism of the failure, the trigger of the avalanche, the slope angle, direction, and elevation.
Loose snow avalanches (far left) and slab avalanches (near center) near Mount Shuksan in the North Cascades mountains. Credit: Thermodynamic/Wikipedia Commons
All avalanches are rated by either their destructive potential or the mass they carry. While this varies depending on the geographical region – – all share certain common characteristics, ranging from small slides (or sluffs) that pose a low risk to massive slides that come that pose a significant risk.
An avalanche has three main parts: the starting zone, the avalanche track, and the runout zone. The starting zone is the most volatile area of a slope, where unstable snow can fracture from the surrounding snowcover and begin to slide. The avalanche track is the path or channel that an avalanche follows as it goes downhill. The runout zone is where the snow and debris finally come to a stop.
Causes:
Several factors may affect the likelihood of an avalanche, including weather, temperature, slope steepness, slope orientation (whether the slope is facing north or south), wind direction, terrain, vegetation, and general snowpack conditions. However, weather remains the most likely factor in triggering an avalanche.
During the day, as temperatures increase in a mountainous region, the likelihood of an avalanche increases. Regardless of the time of year, an avalanches will only occur when the stress on the snow exceeds the strength either within the snow itself or at the contact point where the snow pack meets the ground or the rock surface.
An avalanche east of the town of Revelstoke, BC, in 2010 Credit: Canadian Avalanche Center
Although avalanches can occur on any slope given the right conditions, in North America certain times of the year and certain locations are naturally more dangerous than others. Wintertime, particularly from December to April, is when most avalanches will occur with the highest number of fatalities occurs in January, February and March, when the snowfall amounts are highest in most mountain areas.
Deaths Caused by Avalanches:
In the United States, 514 avalanche fatalities have been reported in 15 states from 1950 to 1997. In the 2002–2003 season there were 54 recorded incidents in North America involving 151 people.
In Canada’s mountainous province of British Columbia, a total of 192 avalanche-related deaths were reported between January 1st, 1996 and March 17th, 2014 – an average of roughly ten deaths per year. During the winter of 2014, avalanche concerns also forced the closure of the Trans-Canada highway on a number of occasions.
Avalanches on Other Planets:
Not too surprisingly, Earth is not the only planet in the Solar System to experience avalanches. Wherever their is mountainous terrain and water ice, which is not uncommon, there is the likelihood that material will come loose and cause a cascading slide to take place.
On February 19th, 2008, NASA’s Mars Reconnaissance Orbiter captured the first ever image of active avalanches taking place the Red Planet. The avalanche occurred near the north pole, where water ice exists in abundance, and was captured by the MRO’s HiRISE (High Resolution Imaging Experiment) camera completely by accident.
Images taken by the MRO’s HiRISE camera show at least four Martian avalanches, or debris falls, taking place near the north pole. Credit: NASA/JPL
The images showed material – likely to include fine-grained ice dust and possibly large blocks – detaching from a towering cliff and cascading to the gentler slops below. The occurrence of the avalanches was spectacularly revealed by the accompanying clouds of fine material (visible in the photographs) that continue to settle out of the air.
The largest cloud (shown in the upper images) was about 180 meters (590 feet) across and extended about 190 meters (625 feet) from the base of the steep cliff. Shadows to the lower left of each cloud illustrate further that these are three dimensional features hanging in the air in front of the cliff face, and not markings on the ground.
The photo was unprecedented because it allowed NASA scientists to get a glimpse of a dramatic change on the Martian surface while it was happening. Despite seeing countless pictures that have detailed the planet’s geological features, most appear to have remained unchanged for several million years. It also showed that terrestrial events like avalanches are not confined to planet Earth.
Scientists at the European Southern Observatory have identified the closest looking solar system to our own. They located a sun-like star more than 100 light years distant with as many as seven different planets, including one that might be the smallest ever found outside the solar system.
“We have found what is most likely the system with the most planets yet discovered,” says Christophe Lovis, lead author of the paper reporting the result. “This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system.”
Some of the planets identified are large but one is only 1.4 times the size of Earth. That’s getting tantalizingly close to finding what astronomers are calling the ‘Holy Grail’ of astronomy, locating a planet just like our own with a breathable atmosphere, moderate temperatures and orbital stability. Scientists have been spotting planets beyond our solar system for the past 15 years, and they’ve now cataloged some 450. They know there are many more out there. The newly found worlds are made essentially of rocks and ice with a solid core. The larger planets probably have a layer of hydrogen and helium gas like Uranus and Neptune and the sixth is possibly a Saturn-like planet.
“We also have good reasons to believe that two other planets are present,” says Lovis. One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered [2], with a mass of about 1.4 times that of the Earth. It is very close to its host star, at just 2 percent of the Earth–Sun distance. One “year” on this planet would last only 1.18 Earth-days.
“This object causes a wobble of its star of only about 3 km/hour — slower than walking speed — and this motion is very hard to measure,” says team member Damien Ségransan. If confirmed, this object would be another example of a hot rocky planet, similar to Corot-7b.
Since the Earth is suspended in space, it cannot be put on a scale and weighed to be compared to other planets. But scientists can estimate its total weight by, among other things, measuring its tug on orbiting satellites. We’ve used this method to weigh the Earth and it turns out to be a whopping 6.6 sextillion tons… that’s two 6s, followed by twenty zeros, or 6,600,000,000,000,000,000,000 tons! But Earth’s weight gain doesn’t stop there… it increases by 100,000 pounds each year from dust and meteoric material falling from the sky. How does this “weigh up” to planetary science?
“Clearly, the exploration of the low-mass planet population has now fully started,” says C. Lovis et al. “The HARPS search for southern extra-solar planets will become the main focus of the field in the coming years. It is expected that the characterization of planetary system architectures, taking into account all objects from gas giants to Earth-like planets, will greatly improve our understanding of their formation and evolution. It will also allow us to eventually put our Solar System into a broader context and determine how typical it is in the vastly diverse world of planetary systems. The characterization of a significant sample of low-mass objects, through their mean density and some basic atmospheric properties, is also at hand and will bring much desired insights into their composition and the physical processes at play during planet formation.”
Many thanks to Dave Reneke of Australasian Science Magazine for sharing and to Mission Green Globe and ESO for the images.
This time lapse footage was taken by astronaut Don Pettit — of Saturday Morning Science and the Zero-G coffee cup fame — during his time on the International Space Station. It shows Earth from day to night and back to day again. Pettit was on the ISS from November 23, 2002 to May 3, 2003, so he was in space when the Columbia accident happened. Pettit is one of the most interesting and quirkier astronauts and I hope he gets to return to the ISS. is scheduled to return to the ISS in 2011 (thanks to Ben H. for clarifying — see comments). This video provides some great views of Earth, especially at night, that can’t be captured with a regular video shot. Stunning.
