Welcome to the moons of Mars, as you’ve never seen them.
NASA’s aging 2001 Mars Odyssey orbiter recently snapped some unique views of the twin moons Phobos and Deimos, in an effort to better understand their texture and surface composition. The images are courtesy of the spacecraft’s THEMIS (the Thermal Emission Imaging System) heat sensitive instrument, and show the thermal gradient across the surface of the moons in color. Odyssey has been studying the moons of Mars since September 2017. The recent images of Phobos taken on April 24, 2019 are especially intriguing, as they occurred during full illumination phase.
For years, NASA’s Mars Odyssey has been working on some night moves. It’s been taking pictures of the Red Planet during nighttime — more than 20,000 in all — to see how the planet’s heat signature looks while the sun is down.
The result is the highest-resolution map ever of the thermal properties of Mars, which you can see here. Why is this important? Researchers say it helps tell the story about things such as if an area is shrouded with dust, where bare bedrock is, and whether sediments in a crater are packed tight or floating freely.
“Darker areas in the map are cooler at night, have a lower thermal inertia and likely contain fine particles, such as dust, silt or fine sand,” stated Robin Fergason at the USGS Astrogeology Science Center in Arizona, who led the map’s creation. Brighter areas are warmer, likely yielding regions of bedrock, crust or coarse sand.
The map from Odyssey’s Thermal Emission Imaging System (THEMIS) is also used for a more practical purpose: deciding where to set down NASA’s next Mars mission.
After assisting in landing site selection for the Curiosity mission, the THEMIS data will be used to figure out where the Mars 2020 rover will be placed, Arizona State University stated.
Researchers at NASA’s Goddard Spaceflight Center and the Massachusetts Institute of Technology have identified a fascinating natural process by which the magnetosphere of our fair planet can — to use a sports analogy — “shot block,” or at least partially buffer an incoming solar event.
The study, released today in Science Express and titled “Feedback of the Magnetosphere” describes new process discovered in which our planet protects the near-Earth environment from the fluctuating effects of inbound space weather.
Our planet’s magnetic field, or magnetosphere, spans our world from the Earth’s core out into space. This sheath typically acts as a shield. We can be thankful that we inhabit a world with a robust magnetic field, unlike the other rocky planets in the inner solar system.
But when a magnetic reconnection event occurs, our magnetosphere merges with the magnetic field of the Sun, letting in powerful electric currents that wreak havoc.
Now, researchers from NASA and MIT have used ground and space-based assets to identify a process that buffers the magnetosphere, often keeping incoming solar energy at bay.
The results came from NASA’s Time History Events and Macroscale Interactions during Substorms (THEMIS) constellation of spacecraft and was backed up by data gathered over the past decade for MIT’s Haystack Observatory.
Observations confirm the existence of low-energy plasma plumes that travel along magnetic field lines, rising tens of thousands of kilometres above the Earth’s surface to meet incoming solar energy at a “merging point.”
“The Earth’s magnetic field protects life on the surface from the full impact of these solar outbursts,” said associate director of MIT’s Haystack Observatory John Foster in the recent press release. “Reconnection strips away some of our magnetic shield and lets energy leak in, giving us large, violent storms. These plasmas get pulled into space and slow down the reconnection process, so the impact of the Sun on the Earth is less violent.”
The study also utilized an interesting technique known as GPS Total Electron Content or GPS-TEC. This ground-based technique analyzes satellite transmitted GPS transmissions to thousands of ground based receivers, looking for tell-tale distortions that that signify clumps of moving plasma particles. This paints a two dimensional picture of atmospheric plasma activity, which can be extended into three dimensions using space based information gathered by THEMIS.
And scientists got their chance to put this network to the test during the moderate solar outburst of January 2013. Researchers realized that three of the THEMIS spacecraft were positioned at points in the magnetosphere that plasma plumes had been tracked along during ground-based observations. The spacecraft all observed the same cold dense plumes of rising plasma interacting with the incoming solar stream, matching predictions and verifying the technique.
Launched in 2007, THEMIS consists of five spacecraft used to study substorms in the Earth’s magnetosphere. The Haystack Observatory is an astronomical radio observatory founded in 1960 located just 45 kilometres northwest of Boston, Massachusetts.
How will this study influence future predictions of the impact that solar storms have on the Earth space weather environment?
“This study opens new doors for future predictions,” NASA Goddard researcher Brian Walsh told Universe Today. “The work validates that the signatures of the plume far away from the Earth measured by spacecraft match signatures in the Earth’s upper atmosphere made from the surface of the Earth. Although we might not always have spacecraft in exactly the correct position to measure one of these plumes, we have almost continuous coverage from ground-based monitors probing the upper atmosphere. Future studies can now use these signatures as a proxy for when the plume has reached the edge of our magnetic shield (known as the magnetopause) which will help us predict how large a geomagnetic storm will occur from a given explosion from the Sun when it reaches the Earth.”
The structure of Earth’s magnetosphere. Credit-NASA graphic in the Public Domain.
Understanding how these plasma plumes essentially hinder or throttle incoming energy during magnetic reconnection events, as well as the triggering or source mechanism for these plumes is vital.
“The source of these plumes is an extension of the upper atmosphere, a region that space physicists call the plasmasphere,” Mr. Walsh told Universe Today. “The particles that make the plume are actually with us almost all of the time, but they normally reside relatively close to the Earth. During a solar storm, a large electric field forms and causes the upper layers of the plasmasphere to be stripped away and are sent streaming sunward towards the boundary of our magnetic field. This stream of particles is the ‘plume’ or ‘tail’”
Recognizing the impacts that these plumes have on space weather will lead to better predictions and forecasts for on- and off- the planet as well, including potential impacts on astronauts aboard the International Space Station. Flights over the poles are also periodically rerouted towards lower latitudes during geomagnetic storms.
“This study defines new tools for the toolbox we use to predict how large or how dangerous a given solar eruption will be for astronauts and satellites,” Walsh said. “This work offers valuable new insights and we hope these tools will improve prediction capabilities in the near future.”
And speaking of which, there’s a common misconception out there that we see reported every time auroral activity makes the news… remember that aurorae aren’t actually caused by solar wind particles colliding with our atmosphere, but the acceleration of particles trapped in our magnetic field fueled by the solar wind.
And speaking of solar activity, there’s also an ongoing controversy in the world of solar heliophysics as to the lackluster solar maximum for this cycle, and what it means for concurrent cycles #25 and #26.
It’s exciting times indeed in the science of space weather forecasting…
and hey, we got to drop in sports analogy, a rarity in science writing!
During the 1950s and just before the great “Space Race” began, scientists like Kristian Birkeland, Carl Stormer, and Nicholas Christofilos had been paying close attention to a theory – one that involved trapped, charged particles in a ring around the Earth. This plasma donut held in place by our planet’s magnetic field was later confirmed by the first three Explorer missions under the direction of Dr. James Van Allen. Fueled by perhaps solar winds, or cosmic rays, the knowledge of their existence was the stuff of nightmares for an uniformed public. While the “radiation” can affect objects passing through it, it doesn’t reach Earth, and this realization quickly caused fears to die. However, there are still many unanswered questions about the Van Allen Radiation Belts that mystify modern science.
Over the years we’ve learned these radiation zones are comprised of electrons and energetically charged particles. We’ve documented the fact they can both shrink and swell according to the amount of solar energy they receive, but what researchers haven’t been able to pinpoint is exactly what causes these responses. Particles come and particles go – but there isn’t a solid answer without evidence. A pertinent question has been to determine if particles escape into interplanetary space when the belts shrink – or do they fall to Earth? Up until now, it’s been an enigma, but a new study employing several spacecraft at the same time has been to trace the particles and follow the trail up.
“For a long time, it was thought particles would precipitate downward out of the belts,” says Drew Turner, a scientist at the University of California, Los Angeles, and first author on a paper on these results appearing online in Nature Physics on January 29, 2012. “But more recently, researchers theorized that maybe particles could sweep outward. Our results for this event are clear: we saw no increase in downward precipitation.”
From October to December 2003, the radiation belts swelled and shrank in response to geomagnetic storms as particles entered and escaped the belts. Credit: NASA/Goddard Scientific Visualization Studio
This isn’t just a simple answer to simple question, though. Understanding the movement of the particles can play a critical role in protecting our satellite systems as they pass through the Van Allen Belts – and its far reaching radiation extensions. As we know, the Sun produces copious amounts of charged particles in the stellar winds and – at times – can blast in our direction during coronal mass ejections (CMEs) or shock fronts caused by fast solar winds overtaking slower winds called co-rotating interaction regions -CIRs). When directed our way, they disrupt Earth’s magnetosphere in an event known as a geomagnetic storm. During a “storm” the radiation belt particles have been known to decrease and empty the belt within hours… a depletion which can last for days. While this is documented, we simply don’t know the cause, much less what causes the particles to leave!
In order to get a firmer grip on what’s happening requires multiple spacecraft measuring the changes at multiple points at the same time. This allows scientists to determine if an action that happens in one place affects another elsewhere. While we look forward to the Radiation Belt Storm Probes (RBSP) mission results, it isn’t scheduled to launch until August 2012. In the interim, researchers have combined data from two widely separated spacecraft to get an early determination of what happens during a loss event.
“We are entering an era where multi-spacecraft are key,” says Vassilis Angelopoulos, a space scientist at UCLA, and the principal investigator for THEMIS and a coauthor on the paper. “Being able to unite a fleet of available resources into one study is becoming more of a necessity to turn a corner in our understanding of Earth’s environment.”
So where did this early support information come from? Fortunately the team was able to observe a small geomagnetic storm which occurred on January 6, 2011. By engaging the the three NASA THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft, two GOES (Geostationary Operational Environment Satellite), operated by the National Oceanic and Atmospheric Administration (NOAA), and six POES (Polar Operational Environmental Satellite), run jointly by NOAA, and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) spacecraft, they were able to catch electrons moving close to the speed of light as they dropped out of the belt for over six hours. Orbiting Earth’s equatorial zones, the THEMIS and GOES spacecraft are just part of the team. The POES spacecraft passes through the radiation belts several times a day as it cruises at a lower altitude and near the poles. By combining data, the scientists were able to take several observational vantage points and proved – without a doubt – that the particles left the belt by way of space and did not return to Earth.
“This was a very simple storm,” says Turner. “It’s not an extreme case, so we think it’s probably pretty typical of what happens in general and ongoing results from concurrent statistical studies support this.”
During this time, the spacecraft also observed a low-density area of the Van Allen belts which appeared along the periphery and traveled inward. This appeared to be an indication the particles were outward bound. If this was a normal occurrence, it stands to reason that a type of “wave” must assist the motion, allowing the particles to reach the outer escape boundary. Discovering just what exactly triggers this escape mechanism will be one of the jobs for RBSP, says David Sibeck at NASA’s Goddard Space Flight Center in Greenbelt, Md., who is NASA’s mission scientist for RBSP and project scientist for THEMIS.
“This kind of research is a key to understanding, and eventually predicting, hazardous events in the Earth’s radiation belts,” says Sibeck. “It’s a great comprehensive example of what we can expect to see throughout the forthcoming RBSP mission.”
