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All lava isn’t the same. There can be tremendous differences in the viscosity (thickness), temperature and chemical composition of lava. The least viscous (least syrupy) lava is known as pahoehoe, and it can flow for many kilometers away from the source of a volcanic eruption. One of the longest flows ever recorded was an eruption from Mauna Loa that was 47 km long.
In fact, when you think of an erupting volcano, with vast rivers of lava flowing out, that’s pahoehoe – it’s a Hawaiian term. It’s a basaltic lava that once hardened has a smooth, ropy surface. In fact, it can have such beautiful shapes that people call it lava sculptures. The strange shapes happen because the front of the lava flow forms a thin shell, and then blobs continually break out from the crust. These cool and then more lava breaks out from that.
Once the pahoehoe lava flows finally cool, the resulting rock is incredibly smooth; they’re smooth down to a scale of just a few millimeters. This is very different to aa lava flows, which feel like jagged glass once they harden. Pahoehoe is smooth and nice to walk across, while a’a lava will ravage your shoes and give you a nasty cut if you happen to fall on it.
We have written many articles about the Earth for Universe Today. Here’s an article about all the different types of lava, and here’s an article about a’a lava.
Thurston Lava Tube on the Big Island of Hawaii. Credit: P. Mouginis-Mark, LPI
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If you’ve ever visited the Big Island of Hawaii, you’ll get a chance to see one of nature’s most amazing formations: a lava tube. Lava tubes are natural tunnels where lava flows underneath the ground, sometimes for many kilometers. After the eruption is over, you can be left with a long empty tunnel that seems almost man made.
A lava tube happens when low viscosity lava forms a continuous hard crust that gets thicker and thicker, while lava is flowing inside it. Eventually the lava forms a thick hard crust above, but low viscosity lava continues to flow inside. In fact, the thick sides act like insulation to keep the inner lava hot and molten. When the eruption finally ends, the lava flows out of the tube, emptying it out.
Lava tubes can be many meters wide, and typically run several meters below the surface. One tube on Mauna Loa starts at the eruption point and then flows about 50 km to the ocean. Inside the tube there can be various formations, like lava stalactites known as lavacicles (named after icicles). You can also get pillars that stretch from the top to the bottom of the lava tube.
Some of the most well known lava tubes are Thurston Lava Tube in Hawaii Volcanoes National Park, and Lava Beds National Monument in Northern California.
We have written many articles about the Earth for Universe Today. Here’s an article about different types of lava. And here’s an article about lava flows in general.
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Volcanoes can erupt with ash and rocks, but one of the most common images are great rivers of molten lava streaming from the volcano’s vent. This molten lava is made of rock, heated to more than 700 degrees C inside the Earth. Inside the Earth, it’s called magma, but when it reaches the surface, scientists call it molten lava.
You might be surprised to know that there are many different kinds of molten lava, depending on the chemical structure of the rock itself. This structure defines how viscous the lava is; how easily it flows. Think of the difference between water and syrup. Syrup is very viscous. Molten lava can be 100,000 times as viscous as water.
The least viscous lava can flow great distances from a volcano during an eruption, sometimes traveling many kilometers, destroying everything in its path. Volcanoes with this kind of molten lava are called shield volcanoes and they take on a very wide, low appearance, since the lava can flow so far. Other types of lava are thicker, or more viscous. It only travels a short distance in thick, crumbling flows. And some molten lava is so thick that it doesn’t really flow at all. It just piles up around the volcanic vent.
When it first erupts from the volcanic vent, molten lava can be anywhere from 700 to 1200 degrees Celsius. The thickness (or viscosity) defines how the lava behaves as it leaves the vent, and how far it can flow downhill before cooling and solidifying. Even though it looks solid, a lava flow can remain hot for weeks and even years before it finally cools.
As scary as it looks, molten lava really isn’t that dangerous for people. You can easily outrun a lava flow. Of course, buildings and trees aren’t so lucky since they’re attached to the ground.
Professor Stephen Hawking in 2006. Credit: Wikipedia
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Physicist/mathematician Stephen Hawking has improved after spending the night at a hospital near his home in Cambridge, England, and the 67-year-old’s condition was described as “comfortable.” Hawking’s first wife, Jane, was quoted that she believed his illness was no longer life-threatening. A spokesperson for Cambridge University, where Prof Hawking holds the post of Lucasian Professor of Mathematics, said that he would be kept in hospital for observation. “He is comfortable and his family is looking forward to him making a full recovery,” said Gregory Hayman. “He has had a good night but will be kept in at Addenbrooke’s Hospital for observation. He is showing signs of improvement.”
Hawking, best known as the author of the best-selling science book A Brief History of Time, was taken to hospital two days after returning from a tour of engagements in the United States. Cambridge University took the unprecedented step of commenting on Hawking’s condition, describing him as “very ill”.
Hawking suffers from ALS (amyotrophic lateral sclerosis), an incurable degenerative disorder also known as Lou Gehrig’s disease. He is wheelchair bound and only able to speak with the help of a voice synthesiser.
He was diagnosed with the muscle-wasting disease at the age of 21, which has gradually robbed him of his voice and movement in his limbs.
At the time of being diagnosed with the disease, he was told that he could expect to live for two years but has become one of the oldest-known survivors of the disease, after more than 40 years.
To commemorate the Hubble Space Telescope’s 19 years in space, the ESA and NASA have released an image of a celestial celebration.
Two members in this trio of galaxies are apparently engaged in a gravitational tug-o-war, giving rise to a bright streamer of newborn blue stars that stretches 100,000 light years across.
Constellation region near ARP 194. Credit: NASA, ESA Z. Levay and A. Fujii
Resembling a pair of owl’s eyes, the two nuclei of the colliding galaxies can be seen in the process of merging at the upper left. The bizarre blue bridge of material extending out from the northern component looks as if it connects to a third galaxy but in reality this galaxy is in the background, and not connected at all.
Hubble’s sharp view allows astronomers to try and sort out visually which are the foreground and background objects when galaxies, superficially, appear to overlap.
The blue “fountain” is the most striking feature of this galaxy troupe and it contains complexes of super star clusters that may have as many as dozens of individual young star clusters in them. It formed as a result of the interactions among the galaxies in the northern component of Arp 194. The gravitational forces involved in a galaxy interaction can enhance the star formation rate and give rise to brilliant bursts of star formation in merging systems.
The stream of material lies in front of the southern component of Arp 194, as shown by the dust that is silhouetted around the star cluster complexes.
The details of the interactions among the multiple galaxies that make up Arp 194 are complex. The system was most likely disrupted by a previous collision or close encounter. The shapes of all the galaxies involved have been distorted by their gravitational interactions with one another.
Arp 194, located in the constellation of Cepheus, resides approximately 600 million light-years away from Earth. Arp 194 is one of thousands of interacting and merging galaxies known in our nearby Universe.
The observations were taken in January 2009 with the Wide Field Planetary Camera 2. Blue, green and red filters were composited together to form the galaxy interaction image.
This picture was issued to celebrate the 19th anniversary of the launch of the Hubble Space Telescope aboard the space shuttle Discovery in 1990. In the past 19 years, Hubble has made more than 880,000 observations and snapped over 570,000 images of 29,000 celestial objects.
Image credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)
Astronomers are announcing a newly discovered exoplanet in the habitable zone of its star, and another one — in the same system — that’s just twice the size of Earth.
The Gliese 581 planetary system now has four known planets, with masses of about 1.9 (planet e, left in the foreground), 16 (planet b, nearest to the star), 5 (planet c, center), and 7 Earth-masses (planet d, with the bluish colour).
This diagram shows the distances of the planets in the Solar System (upper row) and in the Gliese 581 system (lower row), from their respective stars (left). The habitable zone is indicated as the blue area, showing that Gliese 581 d is located inside the habitable zone around its low-mass red star. Based on a diagram by Franck Selsis, Univ. of Bordeaux.
Michel Mayor, a well-known exoplanet researcher from the Geneva Observatory, announced the find today. The planet, “e,” in the famous system Gliese 581, is only about twice the mass of our Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist.
Both planets were discovered by the so-called “wobble method,” using the HARPS spectrograph attached to the 3.6-meter (11.8-foot) ESO telescope at La Silla, Chile.
The gentle pull of an exoplanet as it orbits the host star introduces a tiny wobble in the star’s motion that can just be detected on Earth with today’s most sophisticated technology. Low-mass red dwarf stars such as Gliese 581 are potentially fruitful hunting grounds for low-mass exoplanets in the habitable zone. Such cool stars are relatively faint and their habitable zones lie close in, where the gravitational tug of any orbiting planet found there would be stronger, making the telltale wobble more pronounced.
Many more exoplanets have been discovered using the transit method being employed by NASA’s Kepler mission: as planets pass between their host stars and Earth, they cause an observable, periodic dimming.
Planet Gliese 581 e orbits its host star – located only 20.5 light-years away in the constellation Libra (“the Scales”) — in just 3.15 days.
“With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet,” says co-author Xavier Bonfils from Grenoble Observatory. Being so close to its host star, the planet e is not in the habitable zone. But another planet in this system appears to be.
“Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star,” added team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. “‘d’ could even be covered by a large and deep ocean — it is the first serious ‘water world’ candidate,” he said.
Mayor said it’s “amazing to see how far we have come since we discovered the first exoplanet around a normal star in 1995 — the one around 51 Pegasi. The mass of Gliese 581 e is 80 times less than that of 51 Pegasi b. This is tremendous progress in just 14 years.”
But the astronomers aren’t finished yet. “With similar observing conditions an Earth-like planet located in the middle of the habitable zone of a red dwarf star could be detectable,” says Bonfils. “The hunt continues.”
The findings were presented this week at the European Week of Astronomy & Space Science, which is taking place at the University of Hertfordshire in the UK. The results have also been submitted for publication in the research journal Astronomy & Astrophysics. A preprint is available here.
Source: ESO. (The site also offers numerous videos about the find.)
The design etched to the Pioneer probes. The first interstellar pornography? (NASA)
[/caption]So, you have a radio transmitter and you’ve been tasked to send a message into space to try to communicate with a hypothetical alien civilization. Where do you begin? Probably high on your list is to seek out the best candidate stars to send a signal to. As we only have experience of life on Earth, it’s a pretty good idea to look for Sun-like stars, as for all you know, that is the only place where Life As We Know It™ could exist.
So now you have found the potential location of an alien civilization, what message should you send? Firstly you’d probably want to make a good impression; perhaps sending directions to Earth, a universal map with an arrow pointing at the Solar System. Secondly you might want to identify what/who you are (insert some human physiology here). And third? Perhaps you’d consider sending information about our culture, civilization, history, science; all the good stuff that makes us human.
Would it cross your mind to mention there are 23 bloody conflicts going on right now amongst our own kind? Would you think about telling our potential alien neighbours about what you just had for dinner? Would it be a good idea to tell them about the political corruption in your country, the vast poverty worldwide or the ecological damage we are doing to our own home?
In a recent article written by the director of interstellar message composition at the SETI Institute, the question about communicating honestly with ET, without sanitizing the truth, is asked. Should we really tell an alien civilization about our problems?
Communication with potential alien races is a tricky business (Ian O'Neill)For five decades, the Search for Extraterrestrial Intelligence (SETI) has been scouring the skies for any signal from an intelligent alien civilization. This is a painstaking task that requires much patience and lots of ingenuity. After all, what are we looking for? Assuming extraterrestrial civilizations have worked out how to transmit radio, perhaps we could listen out for that. Unfortunately, apart from the 72 second Wow! signal in 1977, it all seems very quiet out there. If the Drake Equation is to be taken literally, the Milky Way should be teeming with life, some of which should be transmitting their greatest hits right now. There are problems with this theory, as some believe that although aliens might be transmitting, radio signals might not reach us. Perhaps then a sufficiently advanced alien race might be using powerful laser beacons or moving stars to communicate with us. Alas, nothing. Yet.
OK, so let’s turn this around. Perhaps we’ll have more luck if we start transmitting radio signals to Sun-like stars in the hope of an alien race as advanced as ourselves receiving it. This program is known as Messaging Extraterrestrial Intelligence (METI) or “Active-SETI.” But what do we say? One of the earliest messaging attempts was the plaque bolted to the side of the Pioneer spacecraft (pictured top), even though the naked human figures representing male and female caused a stir (some groups considered the naked human form interstellar pornography). Despite a few disputes about what we should be sending into space, generally the messages have been very positive, trying to portray the human race in a very positive light.
Douglas Vakoch, from the SETI Institute in Mountain View, California, disagrees with the policy of sending only positive messages into space via radio transmissions or metal plaques strapped to the sides of spaceships.
“An acknowledgment of our flaws and frailties seems a more honest approach than sending a sanitised, one-sided story,” Vakoch said in a recent New Scientist column. “Honesty is a good starting point for a conversation that could last for generations.”
As the director of interstellar message composition, Vakoch obviously knows a thing or two about sending messages to our potential alien neighbours. However, the question as to whether or not we should sanitize our communications seems a little strange. Of course we should transmit the best mankind has to offer! I don’t believe sending messages of culture, science, mathematics, art and music would be setting us up for a fall. If we are indeed the new kids on the block of extraterrestrial civilizations, I think we’d need to make a great impression (depending on whether ET understands what we are trying to communicate in the first place).
The 1977 Wow! signal (SETI)Vakoch is keen to point out that a sufficiently advanced alien civilization is going to be savvy as to what it takes to be a a galactic race (it’s not all roses after all). If they receive a message from mankind full of positive messages, perhaps they won’t trust us. Worse still, as they get to know us, they think we were hiding our human flaws, misleading them in some way. Therefore, we need to be honest up-front. We need to send the views and opinions of as many people as possible, for good or bad, so extraterrestrial civilizations know what they are dealing with; a talented, yet flawed race.
Unfortunately, that goes against human nature. What’s the first thing you do when moving into a new neighbourhood? You might throw a house-warming party, as a way to introduce yourself to the new neighbours. You probably wouldn’t tell your neighbours about your family/money/alcohol/drug/criminal problems at the party. If you did, you might find the room emptying very quickly. It’s not that you are being dishonest, you’re trying to gain their first-impression trust and interest. This principal holds true for companies trying to sell a product (I have yet to have a doorstep sales person telling me his encyclopaedia collection is actually useless when the world has Wikipedia) and to countries forming new diplomatic ties. We know there’s more to the story than just first impressions, but first impressions are the bonds that help develop the relationship in the future.
Assimilation could be ET's solution to human problemsSo going back to being honest with messaging alien civilizations, if we send “the truth” about our race, we would actually be doing ourselves a disservice. What if the receiving alien civilization doesn’t want to be associated with us as we are considered too aggressive, cruel, greedy or weird?
We can’t second-guess how an extraterrestrial civilization is going to respond to us, there is no precedent of alien communications, so perhaps we should take the “sanitized” approach. Positive information is probably enough information; too much information could turn us into interstellar outcasts before we’ve even had a chance to receive a message from another star. (I thought it was a little too quiet out there, perhaps they received our commercial TV signals.)
According to a new study, less than 10% of the world’s land is more than 48 hours of travel from the nearest city. This doesn’t include air travel, it is ground-travel only (i.e. on foot, train, car, boat, bike, horse, donkey). So no matter where you are in the world, there’s a good chance you can get to somewhere substantially populated within two days. At face-value, this might not seem very important, but when you look at the maps, you see many wilderness locations aren’t quite as remote as we once thought they were. The Amazon Rainforest for example is surprisingly well connected (rivers are quite useful in that respect), and the remote deserts of Africa have a pretty efficient road network.
So, where is the most remote location on Earth? How long would it take to get there?
I can happily say that for 5 months I lived in one of the most remote places in the world. The Norwegian archipelago of Svalbard in the High Arctic turns out to be a very extreme place even if you put the polar bears and -30°C temperatures to one side. No matter how hard you try, it would take 2-3 days by boat to travel from Longyearbyen (on the main island of Spitsbergen) to the Norwegian mainland city of Tromsø. Unfortunately, the number of places around the globe that can boast this are rapidly shrinking.
The fact is, the travel time of any point from the nearest settlement of over 50,000 people using only ground-travel is decreasing rapidly. Transportation infrastructures are spreading and population density is increasing, meaning more people are making bigger cities closer together.
Travel times as used by the researchersA new set of maps created by researchers at the European Commission’s Joint Research Centre in Ispra, Italy, and the World Bank illustrates just how “connected” our world has become and it also highlights the dwindling number of “true” wildernesses.
Based on a computer model that calculates the journey time to the nearest city of 50,000+ people taking only land or water. The variables included in this complex model are types of terrain, road, rail and river network access, altitude, terrain steepness and obstacles (such as border crossings). The key conclusions the researchers gained are that less than 10% of the planet’s landmass is more than 48 hours ground-travel away from the nearest city. The Amazon, for example, only has 20% of its landmass more than 2 days away from the nearest Brazilian city (owed primarily to its vast network of rivers).
The most striking maps include the plotting of the busiest waterways (the English Channel, Mediterranean and South China Seas are the most crowded) and the scope of the world’s road network. In fact, it is little wonder the international community is worried about the increasing numbers of Somalian pirate attacks; another very busy shipping lane is sandwiched between Somalia and Yemen (the key route from the Indian Ocean to the Mediterranean).
The most remote point on the entire planet: 34.7°N 85.7°E - the Tibetan plateauSo where is the most remote place on Earth? The Tibetan plateau (pictured left). From 34.7°N 85.7°E, it would take three whole weeks to travel to the cities of Lhasa or Korla. If you were to take this trip, expect to walk for 20 days and drive by car for one day. Partly due to the rough terrain and 5200 metres in altitude, Tibet will probably remain the most extreme place on Earth for some time to come.
It is hoped these maps will serve as a baseline for future studies, showing how nations deal with population growth, how nature is being eroded and possibly providing some insight as to how to manage the planet a little better than we are at present…
NASA's Mars Exploration Rover Spirit drove 6.98 meters (22.9 feet) southeastward on the 1,871st Martian day, or sol, of the rover's mission on Mars (April 8, 2009). As usual since losing the use of its right-front wheel in 2006, Spirit drove backward, dragging the immobile wheel. Image credit: NASA/JPL-Caltech. Full image and caption
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Poor Spirit. She’s getting old, arthritic and forgetful. The “oldest” of the two Mars Exploration Rovers had another bout of what engineers from JPL are calling “amnesia.” About a week ago, she experienced some unexpected reboots of her computer. Then, she had three good days in a row, completing Earth-commanded activities without incident. But then on April 17 and 18, she became forgetful – she failed to record data into her flash memory (where information is preserved when Spirit is powered down) and rebooted herself again. The last reboot put Spirit into autonomous operation in which the rover keeps itself healthy, and engineers are running diagnostics to try to regain control of the rover.
“We are proceeding cautiously, but we are encouraged by knowing that Spirit is stable in terms of power and thermal conditions and has been responding to all communication sessions for more than a week now,” said JPL’s Sharon Laubach, chief of the rover sequencing team, which develops and checks each day’s set of commands.
Engineers operating Spirit are investigating the reboots, and trying to determine if the amnesia events are related to the reboots. Spirit has had three of these amnesia events in the past 10 days, plus one on Jan. 25. No causal link has been determined between the amnesia events and the reboots.
Engineers have found ways to cope with various symptoms of aging on both rovers. The current diagnostic efforts with Spirit are aimed at either recovering undiminished use of the rover or, if some capabilities have been diminished, to determine the best way to keep using the rover. Spirit driving off into the sunset, a special effects image. credit: NASA/JPL-Caltech/Cornell
Laubach said, “For example, if we do determine that we can no longer use the flash memory reliably, we could design operations around using the random-access memory.” Spirit has 128 megabytes of random-access memory, or RAM, which can store data as long as the rover is kept awake before its next downlink communications session.
During the past week of diagnostic activities, the rover has successfully moved its high-gain dish antenna and its camera mast, part of checking whether any mechanical issues with those components may be related to the reboots, the amnesia events, or the failure to wake up for three consecutive communication sessions two weeks ago.
Spirit and her twin, Opportunity, have been on Mars since 2004. Spirit’s right front wheel is stuck, and so she now drives backwards and drags the crippled wheel behind. The top image shows how the wheel is dragged through the Martian regolith.
It may be a while yet before astronomers agree on a standard model for planet formation around stars. Until recently, after all, Earthlings lacked reliable techniques for glimpsing much beyond our own solar system.
Based on our own backyard, one prevailing theory is that rocky planets like Mercury, Earth and Mars form slowly, close to the sun, from collisions of smaller, solid bodies while gas giants form faster, and farther from the star — often within the first two million years of a star’s life — from smaller rocky cores that readily attract gases.
But new data are suggesting that some gas giants form close to their stars — so close that intense stellar winds rob them of those gases, stripping them back to their cores.
An international research team has found that giant exoplanets orbiting very close to their stars — closer than 2 percent of an Astronomical Unit (AU) — could lose a quarter of their mass during their lifetime. An AU is the distance between the Earth and the Sun.
Such planets may lose their atmospheres completely.
The team, led by Helmut Lammer of the Space Research Institute of the Austrian Academy of Sciences, believes that the recently discovered CoRoT-7b “Super Earth,” which has less than twice the mass of the Earth, could be the stripped core of a Neptune-sized planet.
The team used computer models to study the possible atmospheric mass loss over a stellar lifecycle for exoplanets at orbiting distances of less than 0.06 AU, where the planetary and stellar parameters are very well known from observations.
Mercury is our only neighbor orbiting the Sun in that range; Venus orbits at about .72 AUs.
The 49 planets considered in the study included hot gas giants, planets with masses similar or greater than that of Saturn and Jupiter, and hot ice giants, planets comparable to Uranus or Neptune. All the exoplanets in the sample were discovered using the transit method, where the size and mass of the planet is deduced by observing how much its parent star dims as it the planet passes in front of it.
“If the transit data are accurate, these results have great relevance for planetary formation theories,” said Lammer, who is presenting results at the European Week of Astronomy and Space Science, April 20-23 at the University of Hertfordshire in the UK.
“We found that the Jupiter-type gas giant WASP-12b may have lost around 20-25 percent of its mass over its lifetime, but that other exoplanets in our sample had negligible mass loss. Our model shows also that one major important effect is the balance between the pressure from the electrically charged layer of the planet’s atmosphere and the pressure from the stellar wind and coronal mass ejections (CMEs). At orbits closer than 0.02 AU, the CMEs — violent explosions from the star’s outer layers — overwhelm the exoplanet’s atmospheric pressure causing it to lose maybe several tens of percent of its initial mass during its lifetime.”
The team found that gas giants could evaporate down to their core size if they orbit closer than 0.015 AU. Lower-density ice giants could completely lose their hydrogen envelope at 0.045 AU. Gas giants orbiting at more than 0.02 AU lost about 5-7 percent of their mass. Other exoplanets lost less than 2 percent. Results suggest that CoRoT-7b could be an evaporated Neptune-like planet but not the core of a larger gas giant. Model simulations indicate that larger mass gas giants could not have been evaporated to the mass range determined for CoRoT-7b.
