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Imaggeo on Mondays: Hurricane season, from above

30 Apr

Hurricane Season 2010, distributed by EGU under a Creative Commons licence.

From space, planet Earth resembles a glassy blue marble, a term that was first used to describe a photograph of the Earth taken by the Apollo 17 crew on their way to the moon in 1972. Aside from providing stunning views of our planet, images of the Earth taken from above can also be used for meteorological observations. This beautiful photograph, taken by the Meteosat Second Generation (MSG) satellite, is a case in point.

Maximilian Reuter, who submitted the picture to the Imaggeo database describes it in detail. “This image shows a snapshot of the hurricane season 2010.  It was taken on August 28 that year from the MSG satellite in a geostationary orbit 36,000 km above the equator at 0°E. La Niña conditions favoured lower wind shear over the Atlantic Basin. This allowed storm clouds to grow and organise. Atlantic hurricanes often follow a typical path from Africa across the Atlantic to the east cost of the US. Along this way one can see the Category 4 hurricanes Earl and Danielle as well as the developing tropical storm Fiona. Often the remnants of hurricanes become North Atlantic low-pressure systems which are moving towards Europe.”

Reuter, a researcher at the Institute of Environmental Physics, University of Bremen, also provided a labelled image where the hurricane tracks are highlighted. The image, seen below, is part of the Moments from Space collection. Details on the generation of Moments from Space true-colour images have been published in the International Journal of Remote Sensing.

Highlighted hurricane tracks (source: http://www.moments-from-space.com)

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

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Geosciences column: Promise and challenges of space elevators for tourism

5 Mar

From Star Trek to Arthur C. Clarke, machines that carry humans into space inside a cable-driven chamber – space elevators – have remained in the realm of science fiction. However, recently a Japanese construction company revealed it has aspirations to actually build such a device, claiming it could be operational as early as 2050. Despite assurances from its backers, the project remains scientifically implausible for a number of reasons, not least because travelers would face deadly doses of radiation as they climb through Earth’s atmosphere.

NASA concept model of a space elevator, viewed from space (Source: Wikimedia)

Tokyo-based Obayashi Corp. proposes to carry space tourists to a station a tenth of the distance to the moon, or roughly 36,000km above Earth’s surface, using a solar powered space elevator attached to a carbon nanotube pulley. The device would also allow researchers to continue yet further into space, likely as far as the counterweight at the end of the cable, located a whopping 96,000km from Earth.

Such altitudes are considered very high, even in the context of the most ambitious space projects. For example, the International Space Station orbits at 330km above Earth, whereas the forthcoming Virgin Galactic shuttle will briefly fly customers at an altitude of 110km. In comparison, the average passenger jet cruises at a height of 10km.

But Obayashi is no stranger to ambitious construction projects. They are the main contractor on Tokyo Sky Tree, the world’s tallest self-supporting tower (635m), and its international portfolio includes the Dubai Metro system and Stadium Australia, used for the Sydney Olympics.

“Not simply a dream”

Renewed enthusiasm for the space elevator project hinges on a number of crucial technological developments and methodological insights, including the carbon nanotube technology used to construct the cable. Invented in the 1990s, it is many times stronger and more flexible than steel.

The elevator car, or climber, would travel on the cable using magnetic linear motors, which would use an alternating magnetic field to cause the coil to move. As for the station, it would have to be strategically placed in geosynchronous orbit, that is, circling in sync with the spinning of the Earth, and thereby always remaining in the same spot relative to its base on the ground.

Little is known about many of the project’s finer practical details, including the potential cost, likely sponsors, and where to build it. “At this moment, we cannot estimate the cost for the project,” an Obayashi official said to Wired. “However, we’ll try to make steady progress so that it won’t end up as simply a dream.”

Space tourism has recently been heavily featured in the news, with Virgin Galactic expecting to test its first spacecraft beyond Earth’s atmosphere this year and promising commercial suborbital passenger services as soon as by 2014. However, unlike Virgin Galactic, which will only carry six passengers at a time, its designers claim the elevator could carry up to 30 people and travel at a maximum speed of 200km/h. For comparison, the traditional Space Shuttle travelled at 28,000km/h.

Overview diagram featuring an elevator car (climber) traveling along a reinforced cable towards the counterweight. A recent proposal would place a space station approximately a third of the distance between Earth and the counterweight at the cable's end (Source: Wikimedia)

Avoiding lethal radiation a major challenge

Although the space elevator concept is alluring, the project faces important scientific challenges. For example, without improved protection for travelers, they would be subjected to lethal doses of ionising radiation as they travel through two concentric rings of charged particles surrounding the Earth, known as Van Allen belts.

Van Allen belts span a range of approximately 1,000-20,000 km altitude from Earth’s surface. Therefore, in the proposed space elevator, passengers would spend several days within the belts, exposing them to over 200 times the radiation experienced by the Apollo astronauts. “They would die on the way through the radiation belts if they were unshielded,” said Anders Jorgensen to New Scientist. He is the author of a new study on the subject and a technical staff member at Los Alamos National Laboratory, New Mexico, USA.

Jorgensen’s sentiments are echoed by Iannis Dandouras of the European Space Agency. “The most intense radiation levels are in the Inner Radiation Belt (IRB), which extends typically in altitudes from ~1,000 to ~20,000 km above the equator. At the announced ascension speed of 200km/h, it would take the space elevator passengers almost four days to go through the IRB, receiving during this time an extremely high accumulated radiation dose, which would present a very high risk for their health (or even for their survival, if not properly shielded). The IRB contains a very intense population of energetic ions, trapped in the Earth’s magnetic field, each of these ions having an energy of typically several tens of MeV (megaelectronvolts).  In addition to this, there is also the Outer Radiation Belt, populated mainly by energetic electrons having an energy of typically several MeV, and extending out to almost the geostationary orbit. In the 1960s and 1970s, the Apollo astronauts did not face such a hazard, due to the very quick transit time through the radiation belts (transit through the IRB was less than an hour),” he commented in a recent email interview.

“Humans have long adored high towers”

Proposed solutions to the radiation problem come with important consequences. By moving the elevator’s base off the equator, the most intense part of the radiation belts could be avoided. However, centrifugal forces would cause the elevator’s cable to veer south – if located, for example, at a latitude of 45° North, it would run nearly horizontally for thousands of kilometers through Earth’s atmosphere and thus be weakened by weather-related stresses, such as high winds, hurricanes, and tornadoes.

Another option would be to have a radiation shield stationed along the cable, to be picked up by the elevator when it reaches the belts, but such a shield would be heavy and disrupt the natural motion of the cable.

A further option is to generate magnetic fields around the climber that could shield the habitat module as it climbs through space. However, this would require a great deal of power, difficult to transfer to such altitudes.

NASA has also toyed with the idea of space elevators. According to their concept, the base tower would be approximately 50km tall, with a counterweight placed beyond geostationary orbit – possibly even attached to an asteroid.

Despite the daunting task of overcoming these major practical challenges, Obayashi Corp. remains confident of their ability to deliver humanity’s first space elevator. “We were inspired by the construction of Sky Tree. Our experts on construction, climate, wind patterns, design, they say it’s possible. Humans have long adored high towers. Rather than building it from Earth we will construct it from space,” commented Satomi Katsuyama, the project’s leader, at a recent press conference.

By Edvard Glücksman, EGU Science Communications Fellow  

Geosciences column special: Planetary science, part 2

13 Jan

This month we have a special edition of our Geosciences column with two pieces on planetary science written by external contributors. Whereas the first piece, published yesterday, focused on Martian water, this second article examines the internal structure of the Moon.

If you’d like to contribute to GeoLog, please contact EGU’s Media and Commmunications Officer, Bárbara T. Ferreira at media@egu.eu.


Moon not made of cheese!

A Science paper published last year re-examines previously obtained lunar seismograms to provide evidence that the moon’s core, like that of Earth, has a partly liquid exterior and a solid interior.

Although its surface is barren, the moon's internal configuration is multilayered and resembles Earth's (Source: Wikipedia)

It is likely that, as generations of star-crossed lovers gazed towards the round face of the moon in the night sky, they could not help but wonder what it was made of. “Green cheese” (then referring to freshly made, or immature), as John Heywood proposed in 1546, was probably as good a guess as any. When telescopes allowed a closer view it came with a big disappointment for cheese lovers: all this time, humankind had been staring at a rocky sphere that, furthermore, appeared passive and sterile.

But things are not always as they seem. By re-evaluating data obtained decades ago by the Apollo missions, Renee Weber and her team of planetary scientists at NASA provide, for the first time, a detailed picture of the moon’s interior. Moreover, they show that the moon is remarkably similar to Earth. It comprises a small inner core enclosed by a slightly larger fluid outer core, both of which are surrounded by an even larger partially molten zone, a solid mantle, and finally, a crust.

The Science study relates the polarization of shock waves created by seismic events to the likely internal configuration of the moon. The waves, recorded in the early 1970s, were digitally stacked and filtered, enabling the researchers to better pinpoint the precise point where the shock event took place, determining its velocity and direction. By identifying waves which may have been directed towards the centre of the moon from each area of seismic activity, or cluster zone, and reflected back from the lunar core, the results provide indirect information on the boundaries separating each of the moon’s layers.

Seismic events create different types of waves. Longitudinal, or primary (p-), waves are fast and weak, progressing in a vertical motion, superficially resembling the locomotion of a caterpillar. Shear, or secondary (s-), waves are slower but stronger, and their movement is horizontal, as in the movement of a snake. When p- and s- waves travel in the same direction, they are orientated perpendicular to each other and are polarized.

The waves also differ according to the medium in which they are moving. In fluid, shear waves are attenuated, gradually losing their energy (which is why on Earth we cannot measure direct shear waves from quakes occurring on the other side of the planet, as they would have to pass through its outer core comprising mostly molten iron). This is how Weber and her colleagues were able to indirectly investigate the density of each of the moon’s internal layers.

The recent study would be impossible without data obtained from the Apollo missions, the last of which left the moon in 1972. They left behind enough strategically placed seismic detectors to form a triangle, with edges of over 1,000 km in length, and thus distant enough from each other to pinpoint the location of underground tremors, previously not known to have existed. The lunar Passive Seismic Experiments (PSE), as they were called, continuously recorded five years of data and sent them back to Earth, identifying over 12,000 seismic events, including likely meteorite impacts and moonquakes. These data were reinforced by later research showing that most deep moonquakes occurred repeatedly in particular source regions, located around 1,000 km below the surface, and were associated with constant tidal pressure changes that the moon experiences as it rotates around Earth and the sun.

Plans to place additional seismometers on the moon have thus far been postponed or scrapped and, therefore, the PSE catalogue has remained the only data source for moonquakes. However, as lovers may today still gaze at the moon, at least they can be certain it is not made of cheese.

By Till  F. Sonnemann, researcher at the University of Sydney 

Geosciences column special: Planetary science, part 1

12 Jan

This month we have a special edition of our Geosciences column with two pieces on planetary science written by external contributors. The first article, published today, focuses on Martian water while the second, to be published tomorrow, examines the interior structure of the Moon.

If you’d like to contribute to GeoLog, please contact EGU’s Media and Commmunications Officer, Bárbara T. Ferreira at media@egu.eu.


Martian water lasted longer than previously suspected

There is no liquid water on Mars today, but an article published in Geology late last year suggests some areas of the Red Planet may have held water for longer, and more recently, than scientists previously believed. Mineralogical data gathered by the Mars Reconnaissance Orbiter (MRO), from two troughs in the Noctis Labrynthus area of Valles Marineris, show evidence of the continuous presence of water only two billion years ago. Most other traces of Martian water date back to at least three and a half billion years ago, a significant difference even in geologic time.

“It’s twice as young as other places where water used to exist,” said Catherine Weitz, lead author of the paper and a researcher at the Planetary Science Institute in Tucson, Arizona.

Valles Marineris is a system of canyons running along the equator of Mars. (Source: Wikipedia)

Four billion years ago, Mars was a very different place from the arid red planet we know today. Liquid water could have flowed across the surface of the planet and there may even have been rudimentary life. But unlike Earth, Mars could not sustain this kind of environment and began to dry out. Surface water, along with oxygen and other atmospheric elements, evaporated away into space and temperatures dropped. Now, any water left on Mars is either deep underground or frozen in the small polar ice caps. “It didn’t happen all at once,” Weitz said. “It was a slow process, taking place over hundreds of millions of years.”

Although several deep valleys and troughs on Mars show signs of ancient water, only the two discussed in the Geology article show evidence that water lasted there for more than a very brief time. “It’s the observation of the clays over the sulfates that is interesting and unique to this region,” Weitz said. “It means that water was persistent and in a liquid state for months to years.”

Aside from the clay layering, the researchers also found other lines of evidence that water may once have existed in the Noctis Labrynthus. For example, the presence of hydrated minerals, including silicates like sand and opal, as well as other types of clay, suggests water may once have existed there and at other locations on Mars.

Furthermore, the two troughs in question lie close to the Tharsis, a volcanic plateau home to one of the largest volcanoes in the Solar System. This is important because volcanic activity and tectonic plate movements are often associated with mineral hydration, as ground water is pushed up around and through ore and mineral beds by these powerful events. Even when such water ultimately disappears, traces remain embedded in the area’s mineral structure.

Apart from revealing a unique time frame for the presence of water in the two Noctis Labrynthus troughs, the recent study also suggests its neutral pH differed from the likely acidic water suspected of being present on Mars at the same time. This could be determined by examining the unique mineral layering within the troughs. This finding is significant because water at a neutral pH-level would be theoretically more likely to sustain life.

Putting together the ancient geological history of Mars remotely from Earth is not an easy task, yet MRO’s High Resolution Imaging Science Experiment (HiRISE) and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provide such high-quality images of the Martian surface that researchers can examine, centimetre by centimetre, the minerals in troughs, measuring their spectra for information on their history. “The troughs are in a pretty rugged area high up,” Weitz said. “We wouldn’t be able to get a lander there.”

The study also used data collected by the Viking Mars mission in the 1970s and 80s to measure the age of the area around the troughs by mapping its geology and counting the number of craters. Relatively few craters present there indicate that the local geology stabilized only very recently.

The next step for Weitz and her colleagues will be to try and find other Martian locations with similar characteristics to the ones observed at Noctis Labrynthus. “We have revised some of what we know about water on Mars,” Weitz said. “Now we want to find out more.”

By Eric Hal Schwartz, science writer at the US Environmental Protection Agency

EGU General Assembly 2012 Call for Papers

9 Nov

Abstract submission for the EGU General Assembly 2012 (EGU2012) is now open. The General Assembly is being held from Sunday 22 Apr 2012 to Friday 27 Apr 2012 at the Austria Center Vienna, Austria.

You can browse through the Sessions online.

Each Session shows the link Abstract Submission. Using this link you are asked to log in to the Copernicus Office Meeting Organizer. You may submit the text of your contribution as plain text, LaTeX, or MS Word content. Please pay attention to the First Author Rule.

The deadline for the receipt of Abstracts is 17 January 2012. In case you would like to apply for support, please submit no later than 15 December 2011. Information about the financial support available can be found on the Support and Distinction part of the EGU GA 2012 website.

Further information about the EGU General Assembly 2012 on it’s webpages. If you have any questions email the meeting organisers Copernicus.

Imaggeo on Mondays: Mist Morning Sunrise

1 Aug

Phrao, Thailand. Image by Heike Eichler, distributed by EGU under a Creative Commons License.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Imaggeo on Mondays: Entangled

11 Jul

South auroral oval and polar rain simulated in laboratory using the Planeterrella experiment (J. Lilensten et al., UJF/CNRS, Grenoble, France, online). The Planeterrella was redesigned after K. Birkeland’s original terrella experiments, which in the 1900s helped him unveil the mechanisms at the origin of polar aurorae. A magnetised aluminium sphere is placed in a vacuum chamber. An electric current is then established between the sphere (anode) and the electrode at the top of the figure (cathode) producing emissions in the visible and UV ranges. Image by Cyril Simon Wedlund, distributed by EGU under a Creative Commons License.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Call for Sessions for EGU General Assembly 2012

8 Jul

The public call for sessions for the European Geosciences Union General Assembly 2012 has been issued. The EGU GA 2012 will be held at the Austria Center Vienna (ACV) from 22 April to 27 April 2012. The details are below, the web page to visit to submit sessions is Call for Sessions page of the EGU General Assembly 2012 website.

We hereby invite you, from now until 16 Sep 2011, to take an active part in organizing the scientific programme of the conference.

Please suggest (i) new sessions with conveners and description and (ii) modifications to the skeleton programme sessions. Explore the Programme Groups (PGs) on the left hand side, when making suggestions. Study those sessions that already exist and put your proposal into the PG that is most closely aligned with the proposed session’s subject area.

If the subject area of your proposal is strongly aligned with two or more PGs, co-organization is possible and encouraged between PGs. Only put your session proposal into one PG, and you will be able to indicate PGs that you believe should be approached for co-organization.

If you have questions about the appropriateness of a specific session topic, please contact the Officers for the specific EGU2012 Programme Group. To suggest Union Symposia, Great Debates, Townhall Meetings or Short Courses, please contact the Programme Committee Chair (Gert-Jan Reichart).

In case any questions arise, please contact EGU2012 at Copernicus.