3-D image of a dust grain from Phoenix's Atomic Force Microscope. Credit: NASA/JPL/Caltech/U of Arizona/U of Neuchatel
[/caption]
What is Mars ubiquitous dust really like, close-up? Scientists from the Phoenix missions are finding out with the Atomic Force Microscope (AFM), an instrument that is providing the highest magnification of anything seen from another world. A couple of months ago the Phoenix Mars Lander used its optical microscope to image small grains of the Martian soil. Now, the spacecraft has switched on the AFM to take the first-ever 3-dimensional image of a single particle of Mars’ dust. The AFM can detail the shapes of particles as small as about 100 nanometers, about one one-thousandth the width of a human hair. That is about 100 times greater magnification the optical microscope. The article is rounded, and about one micrometer, or one millionth of a meter, across. It is a speck of the dust that cloaks Mars. Such dust particlets color the Martian sky pink, feed storms that regularly envelop the planet and produce Mars’ distinctive red soil.
“This is the first picture of a clay-sized particle on Mars, and the size agrees with predictions from the colors seen in sunsets on the Red Planet,” said Phoenix co-investigator Urs Staufer of the University of Neuchatel, Switzerland, who leads a Swiss consortium that made the microscope.
“Taking this image required the highest resolution microscope operated off Earth and a specially designed substrate to hold the Martian dust,” said Tom Pike, Phoenix science team member from Imperial College London. “We always knew it was going to be technically very challenging to image particles this small.”
AFM's 8 sharp tips. Image: NASA
The device took about a dozen years to develop. The AFM maps the shape of particles in three dimensions by scanning them with a sharp tip at the end of a spring. During the scan, invisibly fine particles are held by a series of pits etched into a substrate microfabricated from a silicon wafer.
“I’m delighted that this microscope is producing images that will help us understand Mars at the highest detail ever,” Staufer said. “This is proof of the microscope’s potential. We are now ready to start doing scientific experiments that will add a new dimension to measurements being made by other Phoenix lander instruments.”
“After this first success, we’re now working on building up a portrait gallery of the dust on Mars,” Pike added.
Mars’ ultra-fine dust is the medium that actively links gases in the Martian atmosphere to processes in Martian soil, so it is critically important to understanding Mars’ environment, the researchers said. Phoenix's robotic arm scoop brought a sample of soil to MECA, which includes the AFM. Image: NASA/JPL/Caltech/U of Arizona
The particle seen in the atomic force microscope image was part of a sample scooped by the robotic arm from the “Snow White” trench and delivered to Phoenix’s microscope station in early July. The microscope station includes the optical microscope, the atomic force microscope and the sample delivery wheel. It is part of a suite of tools called Phoenix’s Microscopy, Electrochemistry and Conductivity Analyzer.
Close-up view of Enceladus from Cassini's Aug. 11 flyby. Credit" NASA/JPL
Scientists for the Cassini mission called their flyby of Saturn’s small moon Enceladus on August 11 a “skeet shoot,” partially in honor of the current Olympic games underway, but mostly because the spacecraft would be trying to shoot rapidly at the moon with its array of cameras and scientific instruments. As the images begin to stream back, the scientists are definitely excited about what they’re seeing.
“What a dazzling success!” said Carolyn Porco, the Cassini Imaging Team Leader. “There doesn’t even appear to be any smear.” Scientists compared Cassini’s fast flyby of Enceladus to trying to capture a sharp, unsmeared picture of a roadside billboard about a mile away with a 2,000 mm telephoto lens held out the window of a car moving at 50 mph. The imaging team is still poring over the pictures to see if they were successful in “shooting” their target: the active vent regions on the tiger stripe-like features on the moon’s south pole that create the geysers on Enceladus. But the amazingly clear images show a fractured surface littered with boulders and what Porco said could possibly be ice blocks.
Cassini flew over the surface of Enceladus at tremendous speed; about 18 km/sec (about 40,000 mph), which makes taking clear images very difficult. The imaging team devised a technique of turning the spacecraft while taking pictures in rapid succession, shooting at seven, very high priority surface targets. The suite of images ranged in resolution from 8 to 28 meters/pixel, using exposure times that were long enough to see the surface in the twilight near the terminator yet short enough to avoid smear.
Overview of Cassini's flyby. Credit: NASA/JPL
The tiger stripes, officially called sulci, have been identified by the imaging cameras on earlier flybys of Enceladus as the sources of the jets, and also as the “hot spots” or warmer areas on the moon identified by the Cassini’s Composite Infrared Spectrograph.
Porco said the team still has much work to do to decipher all the information in the images and data from the other instruments. “In this painstaking work, we proceed, step by step, to lay bare those things which hold the greatest promise of comprehension, the greatest significance for piecing together the story of the origins of the bodies in our solar system, our Earth, and indeed ourselves,” she wrote in her blog.
We’ll provide further updates on the flyby images as information becomes available.
Images and data from the Mars Reconnaissance Orbiter (MRO) have revealed layers of clay-rich rock that suggests abundant water was once present on Mars. Scientists from the SETI Institute, the Jet Propulsion Laboratory and several universities have been studying data focused on the Mawrth Vallis area on Mars’ northern highland region. This is a heavily cratered, ancient area of the Red Planet whose surface geology resembles a dried-up, river valley through which water may have flowed. While their findings don’t provide evidence for life, it does suggest widespread and long-term liquid water in Mars’ past.
The researchers used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard MRO to examine infrared light reflected from clays situated in the many-kilometer wide channel of Mawrth Vallis.
The infrared spectra from CRISM show an extensive swath of phyllosilicate-bearing material. This is a type of iron and magnesium-rich clay that forms in liquid water, and can be found on Earth in oceans and river beds. It is familiar to anyone who’s nearly broken a shovel while trying to plant a tree. There is also evidence in the spectra for hydrated silica, which in its pure, clean form is known as opal.
The researchers combined their data on the composition of soils in this region with topographic information collected by MOLA, the Mars Orbiter Laser Altimeter, on board the Mars Global Surveyor spacecraft. They found layered aluminum clays lying on top of hydrated silica and iron/magnesium clays. These clays were likely formed when water came in contact with basalt – which is the dominant component of the Martian highlands, and probably was produced from volcanic ash, which once blanketed the planet.
CRISM image overlayed with MOLA data of Mawrth Vallis. This covers an area about 10 kilometers (6.2 miles) wide. Fe/Mg-phyllosilicate is shown in red, Al-phyllosilicate is shown in blue, hydrated silica and an Fe2+ phase are shown in yellow/green.
“We were surprised by the variety of clay minerals in this region,†says Janice Bishop of the SETI Institute. “But what’s interesting is that we find the same ordering of the clay materials everywhere in Mawrth Vallis. It’s like a layer-cake of clays, one on top of another. All these layers are topped with a ‘frosting’ of lava and dust. We can see the clay layers where an impact crater has carved a hole through the surface or where erosion has exposed them.â€
Since phyllosilicates have been found in a number of outcrops on Mars in CRISM images, these new data suggest that whatever mechanism formed clays at Mawrth Vallis has probably operated over much greater areas of the Red Planet. Alteration by liquid water may have been widespread on early Mars.
Bishop is careful to note that this work is part of the long-term effort to establish just how widespread, and for what period of time, liquid water may have existed on Mars.
“This is not evidence for life,†she notes. “But it does suggest the long-term and common presence of liquid water – and concomitant active chemistry – on the Red Planet in the distant past.â€
Artist concept of Cassini flying by Saturn's moon Enceladus. Image credit: NASA/JPL
[/caption]
Saturn’s tiny moon Enceladus is of big interest to planetary scientists trying to understand the dynamics of the moon’s geysers and fissures. On August 11, the Cassini spacecraft will swoop by Enceladus for a close flyby, just 50 kilometers (30 miles) from the surface, with the fractures, or “tiger stripes” near the moon’s south pole, where icy jets erupt as the target of study for the Cassini instruments. “Our main goal is to get the most detailed images and remote sensing data ever of the geologically active features on Enceladus,” said Paul Helfenstein, a Cassini imaging team associate at Cornell University in Ithaca, NY. “From this data we may learn more about how eruptions, tectonics, and seismic activity alter the moon’s surface. We will get an unprecedented high-resolution view of the active area immediately following the closest approach.”
Cassini will actually try to see inside one of the fissures in high resolution, which may provide more information on the terrain and depth of the fissures, as well as the size and composition of the ice grains inside. Refined temperature data could help scientists determine if water, in vapor or liquid form, lies close to the surface and better refine their theories on what powers the jets.
Cassini discovered evidence for the geyser-like jets on Enceladus in 2005, finding that the continuous eruptions of ice water create a gigantic halo of ice and gas around Enceladus, which helps supply material to Saturn’s E-ring. Just after closest approach, all of the spacecraft’s cameras — covering infrared wavelengths, where temperatures are mapped, as well as visible light and ultraviolet — will focus on the fissures running along the moon’s south pole. That is where the jets of icy water vapor emanate and erupt hundreds of miles into space. The image resolution will be as fine as 7 meters per pixel (23 feet) and will cover known active spots on three of the prominent “tiger stripe” fractures.
This will be Cassini’s second flyby of Enceladus this year. During the last flyby in March, the spacecraft snatched up precious samples and tasted comet-like organics inside the little moon. Two more Enceladus flybys are coming up in October, and they may bring the spacecraft even closer to the moon. The Oct. 9 encounter is complimentary to the March one, which was optimized for sampling the plume. The Oct. 31 flyby is similar to this August one, and is again optimized for the optical remote sensing instruments.
The Cassini web page has a mission blog that will follow the fly by, and you can also find images and videos as well.
Latest panorama from Mars. Credit: NASA/JPL/Caltech/U of Arizona
[/caption]
The Phoenix Mars lander finally was successful in delivering a fairly fresh sample of Martian soil to the Thermal and Evolved Gas Analyzer (TEGA) oven on Wednesday and a “bake and sniff” test identified water in the soil sample. “We have water,” said William Boynton of the University of Arizona, lead scientist for TEGA. “We’ve seen evidence for this water ice before in observations by the Mars Odyssey orbiter and in disappearing chunks observed by Phoenix last month, but this is the first time Martian water has been touched and tasted.”
The soil sample came from a trench approximately 2 inches deep. When the robotic arm first reached that depth, it hit a hard layer of frozen soil. Two attempts to deliver samples of icy soil on days when fresh material was exposed were foiled when the samples became stuck inside the scoop. Most of the material in Wednesday’s sample had been exposed to the air for two days, letting some of the water in the sample vaporize away and making the soil easier to handle.
“Mars is giving us some surprises,” said Phoenix principal investigator Peter Smith of the University of Arizona. “We’re excited because surprises are where discoveries come from. One surprise is how the soil is behaving. The ice-rich layers stick to the scoop when poised in the sun above the deck, different from what we expected from all the Mars simulation testing we’ve done. That has presented challenges for delivering samples, but we’re finding ways to work with it and we’re gathering lots of information to help us understand this soil.” Phoenix's Workspace on Mars. Credit: NASA/JPL/Caltech/U of Arizona
Also at the press conference announcing the results, NASA also announced a mission extension for Phoenix, through Sept. 30. The original prime mission of three months ends in late August. The mission extension adds five weeks to the 90 days of the prime mission.
“Phoenix is healthy and the projections for solar power look good, so we want to take full advantage of having this resource in one of the most interesting locations on Mars,” said Michael Meyer, chief scientist for the Mars Exploration Program at NASA Headquarters in Washington.
During the mission extension, the science team will attempt to determine whether the water ice ever thaws enough to be available for biology and if carbon-containing chemicals and other raw materials for life are present.
A full-circle, color panorama of Phoenix’s surroundings was recenlty completed by the spacecraft.
“The details and patterns we see in the ground show an ice-dominated terrain as far as the eye can see,” said Mark Lemmon of Texas A&M University, lead scientist for Phoenix’s Surface Stereo Imager camera. “They help us plan measurements we’re making within reach of the robotic arm and interpret those measurements on a wider scale.”
Project Lucifer. Could the plutonium fuel onboard the Cassini mission cause a nuclear chain reaction on Saturn? Credit: NASA
[/caption] The story: The Lucifer Project is allegedly the biggest conspiracy theory NASA could possibly be involved in. First, back in 2003, the space agency (in co-operation with secret and powerful organizations) dropped the Galileo probe deep into Jupiter’s atmosphere. On board, was a significant quantity of plutonium. As the probe fell though the atmosphere, NASA hoped atmospheric pressures would create an implosion, generating a nuclear explosion thereby kick-starting a chain reaction, turning the gas giant into a second Sun. They failed. So, in a second attempt, they will drop the Cassini probe (again, laden with plutonium) deep into Saturn’s atmosphere in two years time, so this smaller gas giant can succeed where Jupiter failed…
The reality: As investigated briefly in Project Lucifer: Will Cassini Turn Saturn into a Second Sun? (Part 1), we looked at some of the technical problems behind Galileo and Cassini being used as makeshift nuclear weapons. They cannot generate an explosion for many reasons, but the main points are: 1) Tiny pellets of plutonium used to heat and power the probes are in separate, damage-proof cylinders. 2) The plutonium is not weapon grade, meaning the 238Pu makes a very inefficient fissionable fuel. 3) The probes will burn up and break apart, therefore disallowing any chance of lumps of plutonium forming “critical mass” (besides, there is no chance the plutonium could possibly form a configuration to create an implosion-triggered device).
OK, so Galileo and Cassini cannot be used as crude nuclear weapons. But say if there was a nuclear explosion inside Saturn? Could it cause a chain reaction in the core, creating a second Sun?
Thermonuclear bombs The Soviet 50-megaton Tsar Bomba, the largest weapon ever detonated (1961)
Unless nuclear fusion can be maintained within a stellar body, the reaction will very quickly fizz out. So the Lucifer Project proposes Cassini will plunge many hundreds of miles into the atmosphere of Saturn and explode as a crude plutonium-fuelled fission explosion. This explosion will cause a chain reaction, creating enough energy to trigger nuclear fusion inside the gas giant.
I can see where this idea has come from, even though it is inaccurate. The fusion bomb (or “thermonuclear weapon”) uses a fission trigger to kick-start an uncontrolled fusion reaction. The fission trigger is constructed to explode like a normal fission bomb much like the implosion device described in Part 1 of this series. When detonated, huge quantities of energetic X-rays are produced, heating the material surrounding the fusion fuel (such as lithium deuteride), causing the phase transition to a plasma. As very hot plasma is surrounding the lithium deuteride (in a very confined and pressured environment) the fuel will produce tritium, a heavy hydrogen isotope. Tritium then undergoes nuclear fusion, liberating huge quantities of energy as the tritium nuclei are forced together, overcoming the electrostatic forces between nuclei and fusing. Fusion releases large quantities of binding energy, more-so than fission.
How does a star work? A comparison of the size of Jupiter, a brown dwarf, a small star and the Sun (Gemini Observatory/Artwork by Jon Lomberg)
The point that needs to be emphasised here is that in a thermonuclear device, fusion can only be attained when immense temperatures are reached within a very confined and pressurized environment. What’s more, in the case of a fusion bomb, this reaction is uncontrolled.
So, how are nuclear fusion reactions sustained in a star (like our Sun)? In the thermonuclear bomb example above, tritium fusion is achieved through inertial confinement (i.e. rapid, hot and energetic pressure on the fuel to cause fusion), but in the case of a star, a sustained mode of confinement is required. Gravitational confinement is needed for nuclear fusion reactions to occur in the core. For significant gravitational confinement, the star requires a minimum mass.
In the core of our Sun (and most other stars smaller than our Sun), nuclear fusion is achieved through the proton-proton chain (pictured below). This is a hydrogen burning mechanism where helium is generated. Two protons (hydrogen nuclei) combine after overcoming the highly repulsive electrostatic force. This can only be achieved if the stellar body has a large enough mass, increasing gravitational containment in the core. Once the protons combine, they form deuterium (2D), producing a positron (quickly annihilating with an electron) and a neutrino. The deuterium nucleus can then combine with another proton, thus creating a light helium isotope (3He). The outcome of this reaction generates gamma-rays that maintain the stability and high temperature of the star’s core (in the case of the Sun, the core reaches a temperature of 15 million Kelvin).
The proton-proton chain that fuels nuclear fusion inside the core of our Sun. Credit: Ian O'Neill
As discussed in a previous Universe Today article, there are a range of planetary bodies below the threshold of becoming a “star” (and not able to sustain proton-proton fusion). The bridge between the largest planets (i.e. gas giants, like Jupiter and Saturn) and the smallest stars are known as brown dwarfs. Brown dwarfs are less than 0.08 solar masses and nuclear fusion reactions have never taken hold (although larger brown dwarfs may have had a short period of hydrogen fusion in their cores). Their cores have a pressure of 105 million atmospheres with temperatures below 3 million Kelvin. Keep in mind, even the smallest brown dwarfs are approximately 10 times more massive than Jupiter (the largest brown dwarfs are around 80 times the mass of Jupiter). So, for even a small chance of the proton-proton chain occurring, we’d need a large brown dwarf, at least 80 times bigger than Jupiter (over 240 Saturn masses) to even stand the hope of sustaining gravitational confinement.
There’s no chance Saturn could sustain nuclear fusion? Saturn, seen by Cassini. Image credit: NASA/JPL/SSI
Sorry, no. Saturn is simply too small.
Implying that a nuclear (fission) bomb detonating inside Saturn could create the conditions for a nuclear fusion chain reaction (like the proton-proton chain) is, again, in the realms of science fiction. Even the larger gas giant Jupiter is far too puny to sustain fusion.
I have also seen arguments claiming that Saturn consists of the same gases as our Sun (i.e. hydrogen and helium), so a runaway chain reaction is possible, all that is needed is a rapid injection of energy. However, the hydrogen that can be found in Saturn’s atmosphere is diatomic molecular hydrogen (H2), not the free hydrogen nuclei (high energy protons) as found in the Sun’s core. And yes, H2 is highly flammable (after all it was responsible for the infamous Hindenburg airship disaster in 1937), but only when mixed with a large quantity of oxygen, chlorine or fluorine. Alas Saturn does not contain significant quantities of any of those gases.
Conclusion
Although fun, “The Lucifer Project” is the product of someone’s lively imagination. Part 1 of “Project Lucifer: Will Cassini Turn Saturn into a Second Sun?” introduced the conspiracy and focused on some of the general aspects why the Galileo probe in 2003 simply burned up in Jupiter’s atmosphere, scattering the small pellets of plutonium-238 as it did so. The “black spot” as discovered the next month was simply one of the many dynamic and short-lived storms often seen to develop on the planet.
This article has gone one step further and ignored the fact that it was impossible for Cassini to become an interplanetary atomic weapon. What if there was a nuclear explosion inside Saturn’s atmosphere? Well, it looks like it would be a pretty boring affair. I dare say a few lively electrical storms might be generated, but we wouldn’t see much from Earth. As for anything more sinister happening, it is highly unlikely there would be any lasting damage to the planet. There would certainly be no fusion reaction as Saturn is too small and it contains all the wrong gases.
Oh well, Saturn will just have to stay the way it is, rings and all. When Cassini completes its mission in two years time, we can look forward to the science we will accumulate from such an incredible and historic endeavour rather than fearing the impossible…
Update (Aug. 7th): As pointed out by some readers below, molecular hydrogen wasn’t really the cause of the Hindenburg airship disaster, it was the aluminium-based paint that may have sparked the explosion, hydrogen and oxygen fuelled the fire.
Snow Queen is changing! Credit: NASA/JPL/Caltech/U of Arizona
[/caption]
The bright, hard surface feature beneath the Phoenix Mars Lander has visibly changed from when it was first imaged shortly after the lander touched down on the Red Planet. Scientists believe the area, called “Snow Queen” could possibly be ice. Thruster exhaust blew away surface soil covering Snow Queen as Phoenix landed, exposing a hard layer with several smooth, rounded cavities. Phoenix’s Robotic Arm Camera (RAC) took its first close-up image of the area under the lander on May 31, the sixth sol of the mission. Now, more than 60 days since landing, cracks as long as 10 centimeters, or about four inches, have appeared in Snow Queen. A seven-millimeter (less than one-third inch) pebble or clod not seen there before has popped up on the surface, and some smooth texture has subtly roughened. These changes have been occurring slowly. “Images taken since landing showed these fractures didn’t form in the first 20 sols of the mission,” Phoenix co-investigator Mike Mellon of the University of Colorado, Boulder, said. “We might expect to see additional changes in the next 20 sols.”
Mellon said long-term monitoring of Snow Queen and other icy soil cleared by Phoenix landing and trenching operations is unprecedented for science. It’s the first chance to see visible changes in Martian ice at a place where temperatures are cold enough that the ice doesn’t immediately sublimate, or vaporize, away. Phoenix scientists discovered that centimeter-sized chunks of ice scraped up in the Dodo-Goldilocks trench lasted several days before vanishing.
“I’ve made a list of hypotheses about what could be forming cracks in Snow Queen, and there are difficulties with all of them,” Mellon said.
One possibility is that temperature changes over many sols, or Martian days, have expanded and contracted the surface enough to create stress cracks. It would take a fairly rapid temperature change to form fractures like this in ice, Mellon said.
Another possibility is the exposed layer has undergone a phase change that has caused it to shrink. An example of a phase change could be a hydrated salt losing its water after days of surface exposure, causing the hard layer to shrink and crack. “I don’t think that’s the best explanation because dehydration of salt would first form a thin rind and finer cracks,” Mellon said. May 31 image of ice under Phoenix. Credit: NASA/JPL/Caltech/U of Arizone
“Another possibility is that these fractures were already there, and they appeared because ice sublimed off the surface and revealed them,” he said.
As for the small pebble that popped up on Snow Queen after 21 sols — it might be a piece that broke free from the original surface or it might be a piece that fell down from somewhere else. “We have to study the shadows a little more to understand what’s happening,” Mellon said.
Meanwhile, scientists and engineers for the mission are studying the icy soil on Mars, examining how it interacts with the scoop on the lander’s robotic arm, trying different techniques to deliver a sample to the TEGA or Thermal and Evolved Gas Analyzer instrument.
“It has really been a science experiment just learning how to interact with the icy soil on Mars — how it reacts with the scoop, its stickiness, whether it’s better to have it in the shade or the sunlight,” said Phoenix Principal Investigator Peter Smith of the University of Arizona.
Last weekend, the team tried two different methods to pick up and deliver a sample of icy soil to one of the ovens in TEGA. In both cases, most of the sample stuck inside the lander’s scoop, with only a small amount of soil getting into the oven. All the data received from the lander – both images and other data — indicated that not enough soil had been funneled into the oven to prompt the oven to close and begins its analysis.
The team plans to keep gaining experience in handling the icy soil while continuing with other Phoenix studies of the soil and the atmosphere.
Smith said, “While we continue with determining the best way to get an icy sample, we intend to proceed with analyzing dry samples that we already know how to deliver. We are going to move forward with a dry soil sample.”
[/caption]
The Aurora Borealis or Northern Lights are stunningly beautiful. But they can also disrupt radio communications and GPS signals, and even cause power outages. What’s behind the ethereal Northern Lights that causes them to shimmer and dance with colorful lights while sometimes wreaking havoc with electrical systems here on Earth? Using a fleet of five satellites, NASA researchers have discovered that explosions of magnetic energy a third of the way to the moon power substorms that cause sudden brightenings and rapid movements of the aurora borealis, called the Northern Lights. “We discovered what makes the Northern Lights dance,” said Dr. Vassilis Angelopoulos of the University of California, Los Angeles. Angelopoulos is the principal investigator for the Time History of Events and Macroscale Interactions during Substorms mission, or THEMIS.
The cause of the shimmering in Northern Lights is magnetic reconnection, a common process that occurs throughout the universe when stressed magnetic field lines suddenly snap to a new shape, like a rubber band that’s been stretched too far.
“As they capture and store energy from the solar wind, the Earth’s magnetic field lines stretch far out into space. Magnetic reconnection releases the energy stored within these stretched magnetic field lines, flinging charged particles back toward the Earth’s atmosphere,” said David Sibeck, THEMIS project scientist at NASA’s Goddard Space Flight Center. “They create halos of shimmering aurora circling the northern and southern poles.” An explosion of energy increases in the brightness and movement of Northern Lights. Credit: NASA/Goddard Space Flight Center
The data was gathered by five strategically positioned Themis satellites, combined with information from 20 ground-based observatories located throughout Canada and Alaska. Launched in February 2007, the five identical satellites line up once every four days along the equator and take observations synchronized with the ground observatories. Each ground station uses a magnetometer and a camera pointed upward to determine where and when an auroral substorm will begin. Instruments measure the auroral light from particles flowing along Earth’s magnetic field and the electrical currents these particles generate.
During each alignment, the satellites capture data that allow scientists to precisely pinpoint where, when, and how substorms measured on the ground develop in space. On Feb. 26, 2008, during one such THEMIS lineup, the satellites observed an isolated substorm begin in space, while the ground-based observatories recorded the intense auroral brightening and space currents over North America.
These observations confirm for the first time that magnetic reconnection triggers the onset of substorms. The discovery supports the reconnection model of substorms, which asserts a substorm starting to occur follows a particular pattern. This pattern consists of a period of reconnection, followed by rapid auroral brightening and rapid expansion of the aurora toward the poles. This culminates in a redistribution of the electrical currents flowing in space around Earth.
Solving the mystery of where, when, and how substorms occur will allow scientists to construct more realistic substorm models and better predict a magnetic storm’s intensity and effects.
Rendering of the Phoenix Mars Lander with robotic arm working on the Mars surface (NASA)
[/caption]
All the best sci-fi films have them, and they may become our future automated space explorers. Currently, one of the biggest drawbacks for using robots in space is that they depend on human input (i.e. commands need to be sent for every robotic arm motion and every rover wheel rotation). This means that, especially with missions operating far from Earth (such as the Phoenix Mars Lander and Mars Expedition Rovers), very simple and mundane tasks can take hours or even days to complete. One of the main reasons supporting manned exploration of space is that very complex science can be carried out very rapidly (after all, astronauts are human and many robotic operations that take weeks can be completed in seconds). But say if our robotic explorers had a high degree of automation? Say if they could sever the requirement for human input and carry out tasks with intelligent reasoning? As robotic and computer technology increases in sophistication, one Caltech scientist believes space exploration by artificial intelligence is closer than we think…
I remember watching the start of Star Wars: The Empire Strikes Back thinking it was so unfair that Darth Vader and his ilk had access to intelligent space exploration droids that could fly around the galaxy, land on alien worlds and automatically seek out the rebels on Hoth (directing the battle fleet to the icy moon, creating one of the most famous and atmospheric sci-fi battle sequences in movie history. In my opinion at least). But say if we were able to build such “droids” (in fact, droid is a good description of these space explorers, defined as ‘self-aware robots’) that could be sent out into space to explore and report back to mission control without depending on instruction from Earth?
Wolfgang Fink, physicist and researcher at Caltech, believes robotic exploration of space will always take the lead, and even reverse the need for manned missions. “Robotic exploration probably will always be the trail blazer for human exploration of far space,” he says in an interview with Sharon Gaudin. “We haven’t yet landed a human being on Mars but we have a robot there now. In that sense, it’s much easier to send a robotic explorer. When you can take the human out of the loop, that is becoming very exciting.”
While Fink is encouraged by the progress made by missions such as Phoenix and its robotic arm, he is keen to emphasize that the link between human and robot needs to be removed, thus allowing robots to make their own decisions on what science needs to be carried out. In reference to Phoenix’s robotic arm he said, “The arms are the tools, but it’s about the intent to move the arms. That’s what we’re after. To [have the robot] know that something there is interesting and that’s where it needs to go and then to go get a sample from it. That’s what we’ve after. You want to get rid of the joystick, in other words. You want the system to take control of itself and then basically use its own tools to explore.”
An Imperial probe droid from the film Star Wars: Empire Strikes Back (Lucasfilm)
The key attribute robots need to possess is the ability to recognize something of interest, such as a rock or crater, something that a human mind would see as a scientific opportunity. At Caltech, Fink and others are working on programs that use images for robots to distinguish colours, textures, shapes and obstacles. Once artificial intelligence has the ability to do this, if the programming is complex enough, the robot can notice something that is out of place, or a region worth investigating (such as a strangely coloured patch of Mars regolith that a Mars robot will decide to dig into).
As you’d expect, software is being tested and Caltech scientists are beginning to try it out on a rover’s navigation functions. However, the robotic decision-making is very basic presently, but NASA has taken a keen interest in Fink’s work. For example, in 2017 NASA intends to send a robotic mission to Titan, one of Saturn’s moons. In all likelihood the moon will be explored by a balloon-type vehicle. However, it would be impractical for such a vehicle to depend on commands being sent from Earth (as it would take more than an hour for communications to transmit over that distance), so there would need to be a certain degree of automation built into the craft so fast decisions can be made in a dynamic environment such as Titan’s atmosphere.
Although this is all interesting and necessary, there will still be a basic human desire to explore space via manned missions, although a certain degree of self-awareness may be required of our robotic explorers as they carry out reconnaissance trips before we make the trip…
The heliopause is the frontier between the Solar System and the interstellar medium. Credit: NASA/JPL
[/caption]
Space is far from empty. The Solar System can be viewed as a “bubble” of solar matter – filled with particles emitted by the Sun as the solar wind – extending well beyond the orbit of Pluto. The solar wind velocity is supersonic for most of this distance (exceeding a million miles per hour), but the point at which it begins to interact with the interstellar medium (ISM), the solar wind drops to subsonic velocities, creating a region of compression known as the termination shock. After 26 years of flight, the Voyager 1 deep space probe entered this bizarre, turbulent region of space, where solar particles build up and magnetic fields become twisted. Now a new mission has been designed to watch this region of space from afar to begin to understand the boundary of our solar system, where violent turbulence rules and high-energy atoms are generated…
In 2004, Voyager 1 hit it and in 2006, Voyager 2 hit it. The first probe flew through the termination shock at around 94 AU (8 billion miles away); the second measured it at only 76 AU (7 billion miles). This result alone suggests that the termination shock may be irregularly shaped and/or variable depending on solar activity. Before the Voyager missions, the termination shock was theorized, but there was little observational evidence until the two veteran probes traversed the region. The termination shock is of paramount importance to understanding the nature of the outer reaches of the solar system as, counter-intuitively, the Sun’s activity increases, the region beyond the termination shock (the heliosheath) becomes more efficient at blocking deadly cosmic rays. During solar minimum, it becomes less efficient at blocking cosmic rays.
Artist impression of Voyager 1, the first probe to traverse the heliosheath (NASA)
In an effort to map the location and characteristics of the termination shock and heliosheath beyond, NASA scientists are preparing the Interstellar Boundary Explorer (IBEX) for launch in October. IBEX is part of NASA’s Small Explorer program (SMEX), where inexpensive, small probes are used to efficiently observe particular cosmic phenomena. IBEX will be orbiting beyond the influence of the Earth’s magnetic field (the magnetosphere) at a 200,000 mile distance from the Earth. This is because the phenomenon IBEX will be observing can be generated by our own magnetic field. So what will IBEX be measuring? To understand the interaction between solar wind ions and the interstellar medium, IBEX will use two sensors to detect energetic neutral atoms (ENAs) being blasted from the outermost reaches of the solar system.
How are ENAs generated and how are they a measurement of the interaction between the heliosphere and the ISM? Out there in the ISM exists neutral atoms and ions. As the solar system passes through interstellar space, the strong magnetic field generated around the heliosphere deflects the charged ions, pushing them out of the way. However, slow-moving neutral atoms are not affected by the magnetic field and penetrate deep into the heliosheath. When this happens, these neutral atoms from the ISM interact with energetic protons (which do have charge) rapidly spiralling along the magnetic field embedded in the solar wind. When this interaction occurs (known as charge exchange), an electron is stripped from the ISM atom and attracted to the energetic solar wind proton, thus making it neutral. When this exchange occurs, an energetic hydrogen atom (electron and proton) is ejected. An ENA is born.
Artist impression of IBEX (NASA)
Now, this is where the clever bit comes in. As mentioned before, neutral atoms do not “feel” magnetic fields, so when ENAs are created they are ejected in a straight line. Some of these atoms will be directed toward the Earth. IBEX will then measure these ENAs and work out where they came from. As they will have travelled directly to IBEX, the location of the termination shock may be deduced. Over a period of time, IBEX will be able to build up a picture of the locations of these atomic interactions and relate them the characteristics of the boundary of our Solar System.
But the best thing is, we won’t need to send a probe into deep space and wait for decades before it traverses the boundary layer, we will be able to make these measurements from Earth orbit. Such an exciting mission. Roll on the Pegasus rocket launch October 5th, 2008!
