Much of our information about this eruption has come from the European Space Agency’s Envisat satellite, which is a state-of-the-art meteorological instrument in orbit around Earth.  In this article, we’ll take a look at this device, the awesome phenomenon of the eruption itself, and the larger scientific value of studying events like this.

In the study of our planet, we humans are hampered by our very smallness, and the brevity of our lives.  To us, 1821 seems like a long time ago.  If a volcano waits that long between eruptions, we might get a false sense of security- but the people of Iceland have been watching volcanoes for a long time, and they know better.  They know that to a volcano, 1821 was only yesterday.  It’s just long enough for the pressure to build up again- and Iceland has an awful lot of pressure.

The reason is a stroke of amazingly bad luck.  This poor island is the only piece of real estate on the planet that exists directly over not one, but two, of Earth’s pressure vents.

One of these pressure vents is the boundary between two tectonic plates.  America is on one plate and Eurasia is on another.  These plates literally float on the liquid rock of the planet’s mantle, and at the boundary between the two, that liquid rock sometimes seeps through.

Now, there is also another formation called a hotspot, which is made by a huge column of molten rock welling up under the surface.  As you might imagine, this makes the rock above the column bulge up.  If it happens on the ocean floor, it can make an island.

Now, just imagine these two things happening in the same place: a hotspot makes an island right over the boundary between two tectonic plates.  This incredibly unlikely coincidence would create an island which was constantly leaking magma and gases from deep within the Earth.

OK, you don’t have to imagine it; you can just look at the globe.  The winner of our Unluckiest Island in the World Award is Iceland, which is created by an enormous hotspot, and also exactly straddles the Mid-Oceanic Ridge which separates the American tectonic plate from the Eurasian one.  At some unknown time in the future, that column of magma under the hotspot is going to blow, and the resulting eruption will be one of the most destructive events in the life of the planet.

To their great credit, the Icelandic people have made good use of this energy.  Iceland currently leads the world in the generation of electricity by geothermal means.  Sitting on top of a hotspot does have its advantages.

And there’s another good side to all this, if you’re a planetary scientist: Iceland gives you a lot to study.  The island is like a geothermal laboratory where the workings of a planet can be studied in detail.  By looking at Iceland, we can see the interplay of forces that also exist on other small, rocky bodies.  Volcanoes, both active and extinct, have been observed on several other worlds in the solar system.  For instance, Mars has a huge mountain called Olympus Mons (appropriate, don’t you think?) which is a volcanic cone so high that its peak is outside the atmosphere.  Volcanoes have also been observed on some of the system’s moons, and recent evidence indicates that Venus may have active volcanoes, too.  This is one of those lucky instances where Earth presents us with an analog of something that exists on other worlds.  By studying the one we’ve got here, we can, in a way, study the ones out there, too.  The things that we learn about planetary forces and how they interact will also be true on those other worlds.

And that brings us to Envisat.  This satellite, which was designed for studying the weather, has proven invaluable in observing the Eyjafjallajoekull eruption.  This is a good example of a spacecraft that has been adapted to a job which is beyond its originally intended design.

Envisat, launched by the European Space Agency in 2002, is the largest Earth-observing spacecraft ever built.  It is equipped with 10 instruments which perform both optical and radar observations of Earth and give a wealth of data on how the planet works, including factors contributing to global warming.

While a list of all the devices on Envisat would be tedious and exhausting, we can take a look at the two most important ones, both of which are new pieces of technology:

The biggest single instrument on Envisat is called Advanced Synthetic Aperture Radar (ASAR).  It is a significant improvement over any previous meteorological radar unit, with enhanced ability in coverage, range of incidence angles, polarization and modes of operation.  The elevation of the radar beam can be steered, and the observations can be made in swaths of varying width, either 100 or 400 km wide.

MERIS, the Medium Resolution Imaging Spectrometer, is designed to measure the solar radiation reflected by the Earth.  It can observe the entire planet in three days.  Its primary mission is studying the color of the water in oceans and coastal areas.  From this it is possible to derive measurements of chlorophyll pigment concentration in algae, suspended sediment concentration and aerosol loads over marine seas.  In addition, it is used for atmospheric and land monitoring.

Envisat has given us a view of this event that we have never had for any other volcanic eruption.  The satellite, of course, was specifically calibrated for measuring the characteristics of clouds, and a new algorithm had to be devised to adapt it to the volcanic ash plume.  This has been working very well, providing detailed information on the movement, altitude and size of particles involved.  Since the blanket of ash that is spread by an eruption is one of its most destructive aspects, knowing how it moves and where it settles will be of great importance in preparing for future events of this type, and in understanding volcanoes everywhere.

And by studying this one, we are studying a scaled-down model of Olympus Mons on Mars, the volcanoes of Jupiter’s moon Io, and all the other volcanoes of the solar system.  How convenient!

One good thing: amazingly, there have been no casualties from this eruption.  Several hundred households in the vicinity of the volcano had to be evacuated, but all survived.

At this writing (April 24) the eruption is still happening.  The initial plume of ash has subsided enough for air traffic to resume, but it will take days or even weeks to get all those stranded passengers to their destinations.  A news report from two days ago (see sources) says that there are still ominous rumblings coming from the volcano.  Events of this type sometimes continue sporadically for some time, so we may not have heard the last from this one.

Whatever happens, Envisat will be there to watch it.  Thanks to the ESA and their outstanding satellite, future vulcanologists will have an in-depth profile of this eruption to study for years to come.

Sources:

“ESA Observing the Earth: New Satellite Image of Volcanic Ash Cloud, 15 April 2010″ at website of the European Space Agency:  esa.int/esaEO/SEMFYR9MT7G_index_0.html

“ESA Observing the Earth: New Satellite Image of Ash Spewing From Iceland’s Volcano, 19 April 2010″ at website of the European Space Agency:  esa.int/esaEO/SEMM16XN58G_index_0.html

“ESA Missions Observing the Earth: Envisat Overview” at website of the European Space Agency:  esa.int/esaEO/SEMWYN2VQUD_index_0_m.html

“Tremors on the Increase at the Eyjafjallajoekull Volcano” at newspublic:  news-public.com/index.php?option=com_content&view=article&id=1707:tremors-on-the-increase-at-the-eyjafjallajoekull-volcano&catid=34&Itemid=65

“Icelandair reschedules Flights out of Glasgow Despite Keflavik Airport Closure” in IceNews: News From the Nordics 24 April 2010:  icenews.is/index.php/2010/04/24/icelandair-reschedules-flights-out-of-glasgow-despite-keflavik-airport-closure/

This is the story of two such missions, so closely linked that they might be viewed as two parts of the same whole. They are the 2001 Mars Odyssey satellite and the Phoenix lander. As we will see, these two projects were designed to work together, with Odyssey paving the way for Phoenix, then serving as its communication relay. They worked together toward a single goal: proving that there are large deposits of frozen water beneath the Martian surface. In this, they were successful.

This article is the first of two parts. In this one, we will look at the 2001 Mars Odyssey satellite and the science it accomplished. In our next article, we will look at the Phoenix lander. As we will see, their combined effect is a new and better understanding of Mars and its water processes.

The 2001 Mars Odyssey was launched on April 7, 2001 from Cape Canaveral, Florida. It was an ungainly assembly of rods, panels, antennae and other devices, but in general terms, it measured 2.2 meters long, 1.7 meters tall and 2.6 meters wide. At launch, it weighed 725 kilograms, which included the 331.8-kilogram spacecraft, 348.7 kilograms of fuel and 44.5 kilograms of instruments. In an effort to keep the weight down, the satellite’s designers built its framework mostly from aluminum and titanium.

Mars Odyssey carried three instruments:

1. Thermal Emission Imaging System (THEMIS)- would acquire high spatial and spectral resolution images of the surface mineralogy, and provide information on the morphology of the Martian surface. Different elements radiate thermal energy in identifiable patterns, so by studying the thermal emission of the Martian surface, it’s possible to determine which elements are present. A thermal survey would also be able to locate areas of volcanic activity, as well as geothermal zones similar to Yellowstone Park on Earth.

2. Gamma Ray Spectrometer (GRS)- would also contribute to a map of the elemental composition of the surface, and determine the abundance of hydrogen in the shallow subsurface. Hydrogen is used as an indicator of the presence of water.

3. Mars Radiation Environment Experiment (MARIE)- would characterize the Martian near-space radiation environment as related to radiation-induced risk to human explorers.

The two-part plan, mentioned earlier, was present from the beginning. Odyssey was intended to locate areas where frozen water might be present in preparation for a lander which would go down and actually take samples. By mapping the surface morphology and mineralogy, rough areas would hopefully be eliminated from the list of possible landing sites. Once the lander was on the ground, Odyssey would act as its relay to send data back to Earth.

In addition to the presence of hydrogen as an indicator of water, it was expected that the thermal survey would find other signs such as sedimentary deposits of water-soluble minerals in areas where underground ice could have melted and come to the surface at some time in the past. This would provide a long-term history of water activity on the Martian surface.

It is now generally accepted that Mars had large amounts of surface water in its distant history; many of the planet’s land-forms were obviously shaped by flowing water. However, recently there has been a growing body of evidence for the presence of deposits of frozen water on Mars now, not just in the past. For instance, data gathered by the European Space Agency’s Mars Express probe, as discussed in our article from a few weeks ago, strongly indicates that there are large amounts of water frozen just under the surface in some parts of Mars.

Once Mars Odyssey had found some interesting areas, a landing site would be chosen for the lander. This was another job where THEMIS would be useful. Big chunks of rock tend to absorb more heat than the surrounding soil, and retain it longer. Because of this, rocky places would be hotter, and would clearly show up in the thermal survey. Rocky areas tend to be rougher than sandy areas, which would make them too dangerous to be considered as landing sites.

The science to be done by this mission could be summed up as four main goals:

1. Determine whether life ever arose on Mars. Odyssey did not carry instruments to directly detect life, but data gathered by this mission would help to determine whether the Martian environment could have ever supported life. For the first time on Mars, a probe was equipped to map the presence of near-surface water and mineral deposits from past water activity.

2. Characterize the climate of Mars. Odyssey would try to understand the evolution of the Martian climate, and how water activity has effected that evolution.

3. Characterize the geology of Mars. Odyssey would determine the chemical elements that make up the Martian surface, and help explain how the planet’s land-forms developed over time. That information should provide clues to the geological and climatic history of Mars and the likelihood of finding past or present life.

4. Prepare for human exploration. Part of the Odyssey mission, as we mentioned earlier, was the Mars Radiation Environment Experiment. This would determine the levels of harmful radiation on the Martian surface, with the thought of preparing future explorers for the hazards they would face.

The Odyssey mission was a huge success, achieving all of these goals and more. Odyssey entered Mars orbit on October 24, 2001. Over the next 76 days, it performed orbital modifications which finally placed it in a two-hour science orbit. Results started coming in almost immediately. Some of the early data from Odyssey’s THEMIS device showed the presence of chloride mineral deposits in the southern Martian highlands. These are salt beds similar to the ones seen in some areas on Earth, and their presence on Mars means the same thing it means here: there was once a lot of water here. In all, THEMIS found about 200 areas with chloride mineral deposits.

The hydrogen mapping part of the mission was also successful, locating areas with elevated hydrogen levels which indicated a high probability of frozen water just underground.

While the early images of the Martian surface were taken from directly above, with Odyssey looking straight downward, later images were obtained by changing the satellite’s orbit and taking pictures of surface features from an oblique angle. By viewing a spot from directly above, and then shifting the orbit and viewing the same spot from an angle, it was possible to construct three-dimensional images of land-forms.

Here’s another important point: these images not only allow the study of the land-forms of Mars, but also of the atmosphere above them. When the light passes through the air, it is modified by the gas molecules and whatever dust and other particles are in the air. Different sizes and types of particles absorb or reflect light in different ways, so if you subtract the information about the actual ground itself, you are left with a picture of the modifications caused by air molecules and suspended particles. This can tell us a great deal about air currents and the movement of dust etc. in the atmosphere of Mars- factors which can have a huge influence on the climate, and which are necessary for a full understanding of the dynamics of the Martian atmosphere.

As we saw earlier, some of this activity had a specific purpose: locating a landing site for a future lander. A suitable site was found, and in time, the Phoenix lander was launched from Earth. This would provide the final, conclusive piece of evidence: an actual sample of ice taken from the Martian soil. Eventually Phoenix arrived and landed in the place selected for it. During its mission, Mars Odyssey provided the communications link which transmitted the data back to Earth.

But that’s another story, as they say. To find out about Phoenix, you’ll have to read our next article.

Odyssey was also the communication relay for the two famous Mars rovers, Spirit and Opportunity, whose ramblings have provided us with such spectacular pictures and data on the Martian surface.

The Odyssey satellite is still working fine, and will undoubtedly perform other jobs relating to future missions. It is the Energizer Bunny of space probes, still going and going even though its official mission is now over. Hang in there, Odyssey!

In our next article, we will take a closer look at the Phoenix lander and the science it has given us. Don’t miss it!

Sources:
Mars Odyssey: Mission Spacecraft at website of the Jet Propulsion Laboratory, California Institute of Technology: mars.jpl.nasa.gov/odyssey/mission/science/
Mars Odyssey: Mission Science at website of the Jet Propulsion Laboratory, California Institute of Technology: mars.jpl.nasa.gov/odyssey/mission/science/

Mars Odyssey: Mission Overview at website of the Jet Propulsion laboratory, California Institute of Technology: mars.jpl.nasa.gov/odyssey/mission/overview/

Mars Odyssey THEMIS: “New Orbit Gives THEMIS Better Looks at Mars Minerals” at website of Arizona State University: themis.asu.edu/news/new-orbit-gives-themis-better-looks-mars-minerals

Mars Odyssey THEMIS: “Sideways Look From THEMIS Probes Mars’ Atmosphere” at website of Arizona State University: themis.asu.edu/sideways

Mars Odyssey THEMIS: THEMIS Helps Phoenix Land Safely on Mars” at website of Arizona State University: themis.asu.edu/news/themis-helps-phoenix-land-safely-mars

Mars Odyssey THEMIS: Mars Salt Deposit Discovery Points to a New Place to Hunt for Life’s Ancient Traces” at website of Arizona State University: themis.asu.edu/news/mars-salt-deposit-discovery-points-new-place-hunt-lifes-ancient-traces

These three missions are really just variations on the same theme. The probes themselves are very similar to each other, using many of the same kinds of equipment and ground facilities and even some of the same personnel, which made the design and preparatory phases much quicker and easier than if each mission had started from scratch. The word “Express” in the names of the Mars and Venus probes refers to the fact that they were constructed and launched in record time, and with relatively low cost. Besides being stellar achievements in space science (pun intended!) they are also models of the kind of faster and more efficient missions that have become the norm in recent years. These missions prove the point that while space exploration will always be an expensive and lengthy undertaking, there are ways to greatly limit the cost and the amount of time needed for preparation.

Venus Express was launched from Baikonur, Kazakhstan on November 9, 2005 aboard a Soyuz-Fregat launcher. It traveled through space for 155 days, arriving at Venus in April 2006. Its mission was primarily to study the atmosphere and weather patterns on Venus, which are quite different from the kinds of patterns that we see here on Earth, despite the basic physical similarity of the two planets. The mission’s assignments included several firsts on Venus:

1. First global monitoring of the composition of the lower atmosphere in near-infrared transparency “windows.”

2. First coherent study of atmospheric temperature and dynamics at different levels of atmosphere, from the surface up to 200 km.

3. First measurements from orbit of global surface temperature distribution.

4. First study of middle and upper atmosphere dynamics from oxygen and nitrogen oxide emissions.

5. First measurements of non-thermal atmospheric escape.

6. First coherent observations of Venus in the spectral range from ultraviolet to thermal infrared.

7. First application of solar/stellar occultation technique at Venus to analyse how light is absorbed by the atmosphere, revealing atmospheric characteristics.

8. First use of 3D ion mass analyser, high-energy resolution electron spectrometer and energetic neutral atom imager.

9. First sounding of top-side ionospheric structure.

Venus Express was designed to address several open questions suggested by previous research. One of the most baffling mysteries is the cause of the super-fast atmospheric rotation and hurricane-force winds that have been observed on Venus. The Venusian atmosphere is whipping around the planet in a vast, global motion that is more than 60 times the speed of the planet’s rotation. This is a mystery, since such rapid motion cannot be explained by any conventional theory of atmospheric dynamics. Venus Express was designed to study the atmosphere in an effort to discover where all that energy is coming from. Another mystery is the double atmospheric vortex that has been observed at both Venusian poles, and has persisted for the entire observation period. The fact that similar features exist at both of the Venusian poles indicates a global symmetry that has so far eluded explanation. Scientists do not know how these features maintain their shape, and will be observing them closely in an attempt to figure out their dynamics.

Another part of Venus Express’ mission was the study of certain mysterious ultraviolet markings that have been seen at the tops of Venusian clouds. The upper clouds have areas visible in the ultraviolet that mysteriously absorb half of the solar energy received by the planet. The origin of these markings, and their remarkable absorption power, were among the questions being asked by Venus Express.

While the probe was designed to study the composition and dynamics of the Venusian atmosphere, it is also able to gain some information about the surface underneath that atmosphere. For instance, one of the questions regarding Venus is the nature and extent of volcanic activity on the planet, and how recently that activity occurred. Because it is capable of compiling detailed data on the temperature distribution and chemical composition of the atmosphere, Venus Express is capable of sensing both the heat of a volcanic eruption, and the chemicals that such an eruption would release into the air. By doing this, the probe should be able to spot places where eruptions have happened recently and determine how frequently they have occurred. In addition, Venus Express should be able to obtain valuable data on surface temperature, mineralogy, chemical weathering and the occurrence of earthquakes.

Since Venus Express has been in orbit around Venus for some time now, it has been able to obtain preliminary data on some of these questions. The picture that is emerging is of a planet that has changed radically from its earlier days. While Venus is hot and dry today, there is growing evidence that it may have been much more earthlike in its infancy.

For instance, Venus Express has observed that there is a color difference between the highland regions of Venus and the lowlands. On Earth, such a color difference would indicate that the highlands are composed primarily of granite. Granite is a relatively light rock formed by the action of water on basalt. In order for large amounts of granite to be present on the planet today, there must have been a lot of water sometime in the past.

In fact, theories of planetary formation would lead us to think that Venus and Earth started out with similar amounts of water. The two planets were formed from the same protoplanetary material, and were subjected to the same cometary bombardment in the early history of the solar system. Because of this, there is every reason to think that the two planets were once much more similar than they are today.

On Earth, granite literally floats on the heavier molten rock underneath, and forms the basis of the continents. So, when we look at Venus today and see highland regions that resemble the continental masses of Earth, the obvious conclusion is that these are the ancient continents of Venus, and that they were once surrounded by oceans as extensive as those on Earth. We are looking back billions of years, to a time when Venus, once called “Earth’s twin,” may have really deserved that title.

The question is unavoidable: was there life? Given the data that we have at the moment, we can’t answer that question- but it certainly is an intriguing possibility.

There is also some new data on the UV markings at the polar regions. It has been determined that these are caused by plumes of UV-absorbing material that has been brought up from deep in the atmosphere by convection currents. In other words, these UV-absorbing regions are really just the tops of tall columns of material. Where they well up, areas of high absorption are created, and the areas where they do not appear remain UV bright. That’s the phenomenon that is taking place, but the reason for it, and the exact nature of the absorbing material, are still unknown.

In regard to the vortexes at the north and south poles, we now know that they are much more variable than was originally thought. Observations on successive orbits have shown that the formations change their shape quickly and extensively, sometimes forming two separate “eyes” and sometimes a single oval or circular formation. A classic “eye of the hurricane” shape has been observed at the center of the south polar vortex. The dynamics of these features seem to be very complex, and will warrant much observation in the future.

Venus Express has also seen an eerie infrared glow in the night-time atmosphere of Venus, caused by nitric oxide which is produced when the sun’s radiation bombards the atmosphere and breaks up molecules, which recombine and release energy in the form of infrared light. This night glow can tell us much about the composition and movement of the atmosphere.

These are only a few of the things being learned from Venus Express. A full discussion of the data is far beyond the scope of this humble article. (For those who want more detail, the ESA website provides fascinating reading.) The probe continues to function well, and its mission has now been extended through December of 2012. Considering the huge success of the mission so far, we can only expect more great things in the future.

As new data comes in, it will be covered here. Watch this site for updates.

Sources:

Space Topics: Venus Express at website of the Planetary Society: planetary.org/explore/topics/venus_express/

Venus Express mission page at ESA website: esa.int/esaMI/Venus_Express/index.html

Venus Express Education and Outreach website maintained by the University of Wisconsin-Madison: venus.wisc.edu/

Malik, Tariq: A Cloudy Target: Europe’s Venus Probe to Explore Shrouded Planet at SPACE.com: space.com/businesstechnology/051026_techwed_venusexp.html

A sudden loss of signal unexpectedly took place just before the closest approach, but this now appears to have been a safety measure taken by the onboard fault-management system, and did not result in a loss of important data, as was originally feared. It happened during an eighteen minute period when the probe was being eclipsed by the shadow of Mercury. With solar power temporarily cut off, the probe was supposed to operate on its own internal batteries during this time, but ten minutes after entering eclipse and four minutes before the closest approach point, the signal from the probe stopped.

According to Eric Finnegan of the Johns Hopkins Applied Physics Laboratory, the spacecraft had autonomously switched itself to a safe operating mode due to an unexpected configuration of the power system during the eclipse. While in this safe mode, the probe preserved all data on its solid-state recorder. When the probe came out of eclipse, it returned to operational mode and began transmitting the stored data to Earth. All the data have now been received, and are being analyzed to confirm the full sequence of events.

It now appears that the main purpose of the flyby, the gravity assist to alter the probe’s orbit, was completely successful. In addition, all of the observational data from the approach have been retrieved, including pictures of previously unseen terrain.

This was MESSENGER’s final flyby of Mercury. For the next 18 months, the probe and the planet will move in their respective orbits, and when they approach each other again, MESSENGER will not flyby, but instead will go into orbit around the planet. From that vantage point, it will be able to observe the planet in unprecedented detail.

It will be the culmination of a mission that has been a model of success from the start. MESSENGER was launched on August 3, 2004, the first probe to be sent to Mercury since the Mariner 10 flyby 33 years earlier. The planned course would be an ambitious voyage through the inner solar system, with course modifications provided by one flyby of Earth, two flybys of Venus and three flybys of Mercury.

The first of the Mercury encounters happened on January 14, 2008. In it, MESSENGER passed 200 kilometers from the planet, imaging portions of the surface that had never been seen before and collecting a wide array of scientific observations, including magnetometer readings and spectrographic data. The second flyby took place on October 6, 2008. Again the probe passed about 200 kilometers from the surface, and took advantage of the opportunity to make further observations.

The third flyby was the closest, bringing the probe within about 140 miles of Mercury’s surface. On this one, Mercury still had a few surprises. One of these was a double-ringed impact basin 180 miles across. The shape of the feature is remarkably well preserved, indicating that it is probably relatively young, perhaps only a billion years old. That’s unusual, since most impact craters date to the early days of the solar system, some four billion years ago. The inner floor of this basin is of a different color from its surroundings, and appears to be even younger than the rest of the feature. This may be the youngest volcanic material on Mercury.

Spectrographic observations performed on the third flyby also revealed that the surface material on Mercury is rusty. It contains a high percentage of iron oxide, which provides the answer to an earlier puzzle. Previous observations had indicated that there was a low amount of iron on the surface, which was a surprise for a small, rocky planet. Now we know that the iron is there after all; it’s just locked up in those oxides.

This flyby also provided the chance for further observations of Mercury’s magnetic field and its exosphere (extremely thin atmosphere) and the first detailed scans of the north and south poles. These polar regions will be a great source of interest when MESSENGER settles into its final orbit around the planet, since there is at least a slight possibility that they could contain water. This amazing possibility is due to a paradox: since Mercury keeps the same face toward the sun at all times, its dark side- and particularly the polar regions- may have some of the coldest real estate in the solar system. As incredible as it seems, Mercury may have ice that has been frozen since the planet’s birth.

That’s just one of the many questions that will be addressed when MESSENGER and Mercury come back together and the probe goes into its permanent orbit. When that happens, we will start to really get acquainted with the sun’s closest planet, until recently the least explored body in the solar system.