This image from the Cassini spacecraft, shows a huge arrow-shaped storm measuring 1,500km in length. Image Credit: NASA/JPL/SSI
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Titan is making news again, this time with Cassini images from 2010 showing a storm nearly as big as Texas. Jonathan Mitchell from UCLA and his research team have published their findings which help answer the question:
What could cause such large storms to develop on a freezing cold world?
For starters, the huge arrow isn’t a cosmic detour sign reminding us to “Attempt No Landings” on Jupiter’s moon Europa.
In the study by Mitchell and his team, a model of Titan’s global weather was created to understand how atmospheric waves affect weather patterns on Titan. During their research, the team discovered a “stenciling” effect that creates distinct cloud shapes, such as the arrow-shaped cloud shown in the Cassini image above.
“These atmospheric waves are somewhat like the natural, resonant vibration of a wine glass,” Mitchell said. “Individual clouds might ‘ring the bell,’ so to speak, and once the ringing starts, the clouds have to respond to that vibration.”
Titan is the only other body in the solar system (aside from Earth) known to have an active “liquid cycle”. Much like Titan’s warmer cousin Earth, the small moon has an atmosphere primarily composed of Nitrogen. Interestingly enough Titan’s atmosphere is roughly the same mass as Earth’s and has about 1.5 times the surface pressure. At the extremely low temperatures on Titan, hydrocarbons such as methane appear in liquid form, rather than the gaseous form found on Earth.
With an active liquid both on the surface and in the atmosphere of Titan, clouds form and create rain. In the case of Titan, the rain on the plain is mainly methane. Water on Titan is rock-hard, due to temperatures hovering around -200 c.
Studies of Titan show evidence of liquid runoff, rivers and lakes, further emphasizing Titan’s parallels to Earth. Researchers believe better understanding of Titan may offer clues to understanding Earth’s early atmosphere. In another parallel to earth, the weather patterns on Titan created by the atmospheric waves can create intense rainstorms, sometimes with more than 20 times Titan’s average seasonal rainfall. These intense storms may cause erosion patterns that help form the rivers seen on Titan’s surface. Mitchell described Titan’s climate as “all-tropics”, basically comparing the weather to what is usually found near Earth’s equator. Could these storms be Titan’s equivalent of monsoon season?
Mitchell stated “Titan is like Earth’s strange sibling — the only other rocky body in the solar system that currently experiences rain”. Mitchell also added, “In future work, we plan to extend our analysis to other Titan observations and make predictions of what clouds might be observed during the upcoming season”.
The research was published Aug. 14 in the online edition of the journal Nature Geoscience .
Phobos, one of the two natural satellites of Mars silhouetted against the Martian surface. Credit: ISRO
Mars Express images of Phobos from January 9, 2011 flyby
If someone were to ask you when fear was first discovered, you could tell them August 11, 1877. That’s when, 134 years ago today, Asaph Hall identified Phobos, the larger of Mars’ two moons. But even though it’s named after the Greek god of fear, there’s nothing to be afraid of…
Phytoplankton bloom in the Barents Sea. Credit: NASA/Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite
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Phytoplankton are tiny, microscopic plant-like organisms, but when they get together and start growing they can cover hundreds of square kilometers and be easily visible in satellite images. This image of the Barents Sea was taken on August 14, 2011 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. When conditions are right, phytoplankton populations can grow explosively, a phenomenon known as a bloom. A bloom may last several weeks, but the life span of any individual phytoplankton is rarely more than a few days. The area in this image is immediately north of the Scandinavian peninsula. Blooms spanning hundreds or even thousands of kilometers occur across the North Atlantic and Arctic Oceans every year. But, said Jeff Schmaltz from NASA’s Earth Observatory website, seeing such a wide area without clouds during the bloom is a rare treat.
Phytoplankton thrive in cold ocean waters, which tend to be rich in nutrients. Schmaltz said the milky blue color is an indicator that the bloom probably contains coccolithophores, which are plated with white calcium carbonate. Seen through ocean water, a coccolithophore bloom is bright blue. Other shades may be from other species of phytoplankton.
Yippee! This is the way I feel whenever I see the International Space Station passing overhead! Astrophotographer Pete Glastonbury from the UK posted this picture on my Facebook page when I mentioned what a great ISS pass I had just seen. In describing the image, Pete said, “My daughter Sammy suggested we use the trampoline to create the photo as a way to illustrate our desire to get into space.”
Lovely!
Want to get your astrophoto featured on Universe Today? Join our Universe Today Flickr group; we select photographs from this group and post them every day. If you don’t want to join Flickr, you can send your images in by email. If you do contribute to the group, or send us photos by email, you’re giving us permission to post them here on Universe Today. To help us out, please explain what’s in the picture, when you took it, the equipment you used, and/or a little story about it — that would enable us to write a better article about your picture! Make sure you tell us your name, and give us a place we can link to if people want to see more of your work.
We just received a note from Andrew Franknoi and the Astronomical Society of the Pacific that they are making available, free of charge, 30 audio and video podcasts from talks given by distinguished astronomers on the latest ideas and discoveries in the field. Speakers include:
* Frank Drake, who began the experimental search for intelligent life among the stars,
* Mike Brown, who discovered most of the dwarf planets beyond Pluto (and whose humorous talk is entitled “How I Killed Pluto and Why it Had it Coming”),
* Natalie Batalha, project scientists on the Kepler Mission to find Earths around other stars,
* Alex Filippenko (national professor of the year) on finding black holes.
Recent topics added to the offerings include: multiple universes, Saturn’s moon Titan (with an atmosphere, rivers, and lakes), our explosive Sun, and whether we should expect doomsday in 2012.
The talks are part of the Silicon Valley Astronomy Lectures, jointly sponsored by NASA’s Ames Research Center, the Astronomical Society of the Pacific, the SETI Institute, and Foothill College.
They are available via the web and ITunes. For a complete list and to begin listening, go to: http://www.astrosociety.org/education/podcast/
If you’re a space buff, you’ve probably seen IMAX movies like Space Station 3-D or IMAX Hubble 3-D. Those movies require huge, cumbersome cameras to be sent to space and back again, along with lots of editing and processing to create the 3-D effect you can only see in theaters. Now, with a new camera on board the ISS, astronauts can stream live 3-D video back to Earth, showing what it’s like to live and work in space like never before, and it can be seen on your computer screen or television. Continue reading “First Live 3-D Video From Space”
Comet C2009 P1 Garradd and Perseids imaged by students at Bareket Observatory.
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What are you waiting for? If it’s an engraved invitation, then consider this your pass to get out and start looking for Comet C/2009 P1 Garradd! It’s well within reach of average binoculars and it’s even in a position that’s easy for the average observer! Step on out here into the backyard and I’ll show you…
At close to magnitude 8, Comet C/2009 P1 Garradd is currently grazing its way along the eastern line of the Summer Triangle. Even if you live in a moderately light polluted area, you should be able to make out the three bright stars, Deneb to the north, Vega to the west and Altair to the south. Just aim your binoculars roughly halfway between Altair and Deneb and begin scanning on binocular field at a time for a faint, fuzzy poofball that signifies the comet’s presence. What you will see in binoculars will appear to be like a “fuzzy star” – while a telescope will reveal the beginnings of a tail.
Comet Elenin -- the little fuzzy blob in the middle of the image -- as it appeared on May 22, 2011. Credit: Peter Lake
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Lord knows, we’ve tried. We’ve featured a couple of articles about Comet Elenin to try and answer questions and allay any fears about this comet; how it will just pass by Earth — harmlessly at 35 million km (22 million miles) at its closest approach — and an FAQ showing how much of the “information” being dished out by breathless scaremongers of how the comet will hit Earth, or cause Earthquakes and floods, or block out the Sun, and the dangers are being covered up by the government is just plain rubbish. But the questions and panic keep coming to our inboxes and in the comments sections of our articles. Scientists at NASA have been bombarded with questions as well, so they have now put together a list of the most asked questions they’ve received, with various scientists answering the questions. Bottom line: Comet Elenin poses no threat to Earth.
Before the questions, just a little info about Comet Elenin, also known by its astronomical name C/2010 X1. The comet was first detected on Dec. 10, 2010 by Leonid Elenin, an observer in Lyubertsy, Russia, who made the discovery “remotely” using an observatory in New Mexico. At that time, Elenin was about 401 million miles (647 million kilometers) from Earth. Since its discovery, Comet Elenin has – as all comets do – closed the distance to Earth’s vicinity as it makes its way closer to perihelion, its closest point to the Sun.
Compiled below are the some of the most-asked questions, with answers from Don Yeomans of NASA’s Near-Earth Object Program Office at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and David Morrison of the NASA Astrobiology Institute at the NASA Ames Research Center in Moffett Field, Calif.
When will Comet Elenin come closest to the Earth and appear the brightest?
Comet Elenin should be at its brightest shortly before the time of its closest approach to Earth on Oct. 16, 2011. At its closest point, it will be 22 million miles (35 million kilometers) from us.
Will Comet Elenin come close to the Earth or between the Earth and the moon?
Comet Elenin will not come closer to Earth than 22 million miles (35 million kilometers). That’s more than 90 times the distance to the moon.
Trajectory of comet Elenin. Image credit: NASA/JPL-Caltech
Can this comet influence us from where it is, or where it will be in the future? Can this celestial object cause shifting of the tides or even tectonic plates here on Earth?
There have been incorrect speculations on the Internet that alignments of comet Elenin with other celestial bodies could cause consequences for Earth and external forces could cause comet Elenin to come closer. “Any approximate alignments of comet Elenin with other celestial bodies are meaningless, and the comet will not encounter any dark bodies that could perturb its orbit, nor will it influence us in any way here on Earth,” said Don Yeomans, a scientist at NASA JPL.
“Comet Elenin will not only be far away, it is also on the small side for comets,” said Yeomans. “And comets are not the most densely-packed objects out there. They usually have the density of something akin to loosely packed icy dirt.
“So you’ve got a modest-sized icy dirtball that is getting no closer than 35 million kilometers [about 22 million miles),” said Yeomans. “It will have an immeasurably miniscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”
I’ve heard about three days of darkness because of Comet Elenin. Will Elenin block out the sun for three days?
“As seen from the Earth, comet Elenin will not cross the sun’s face,” says Yeomans.
But even if it could cross the sun, which it can’t, astrobiologist David Morrison notes that comet Elenin is about 2-3 miles (3-5 kilometers) wide, while the sun is roughly 865,000 miles (1,392,082 kilometers) across. How could such a small object block the sun, which is such a large object?
Let’s think about an eclipse of the sun, which happens when the moon appears between the Earth and the sun. The moon is about 2,500 miles (4,000 kilometers) in diameter, and has the same apparent size as the sun when it is about 250,000 miles (400,000 kilometers) away — roughly 100 times its own diameter. For a comet with a diameter of about 2-3 miles (3-5 kilometers) to cover the sun it would have to be within 250 miles (400 kilometers), roughly the orbital altitude of the International Space Station. However, as stated above, this comet will come no closer to Earth than 22 million miles.
I’ve heard there is a “brown dwarf” theory about Comet Elenin. Would its mass be enough to pull Comet Honda’s trajectory a significant amount? Could this be used to determine the mass of Elenin?
Morrison says that there is no ‘brown dwarf theory’ of this comet. “A comet is nothing like a brown dwarf. You are correct that the way astronomers measure the mass of one object is by its gravitational effect on another, but comets are far too small to have a measureable influence on anything.”
If we had a black or brown dwarf in our outer solar system, I guess no one could see it, right?
“No, that’s not correct,” says Morrison. “If we had a brown dwarf star in the outer solar system, we could see it, detect its infrared energy and measure its perturbing effect on other objects. There is no brown dwarf in the solar system, otherwise we would have detected it. And there is no such thing as a black dwarf.”
Will Comet Elenin be visible to the naked eye when it’s closer to us? I missed Hale-Bopp’s passing, so I want to know if we’ll actually be able to see something in the sky when Elenin passes.
We don’t know yet if Comet Elenin will be visible to the naked eye. Morrison says, “At the rate it is going, seeing the comet at its best in early October will require binoculars and a very dark sky. Unfortunately, Elenin is no substitute for seeing comet Hale-Bopp, which was the brightest comet of the past several decades.”
“This comet may not put on a great show. Just as certainly, it will not cause any disruptions here on Earth. But, there is a cause to marvel,” said Yeomans. “This intrepid little traveler will offer astronomers a chance to study a relatively young comet that came here from well beyond our solar system’s planetary region. After a short while, it will be headed back out again, and we will not see or hear from Elenin for thousands of years. That’s pretty cool.”
This comet has been called ‘wimpy’ by NASA scientists. Why?
“We’re talking about how a comet looks as it safely flies past us,” said Yeomans of NASA’s Near-Earth Object Program Office. “Some cometary visitors arriving from beyond the planetary region – like Hale-Bopp in 1997 — have really lit up the night sky where you can see them easily with the naked eye as they safely transit the inner-solar system. But Elenin is trending toward the other end of the spectrum. You’ll probably need a good pair of binoculars, clear skies and a dark, secluded location to see it even on its brightest night.”
Why aren’t you talking more about Comet Elenin? If these things are small and nothing to worry about, why has there been no public info on Comet Elenin?
Comet Elenin hasn’t received much press precisely because it is small and faint. Several new comets are discovered each year, and you don’t normally hear about them either. The truth is that Elenin has received much more attention than it deserves due to a variety of Internet postings that are untrue. The information NASA has on Elenin is readily available on the Internet. (See http://www.jpl.nasa.gov/news/news.cfm?release=2011-135) If this comet were any danger to anyone, you would certainly know about it. For more information, visit NASA’s AsteroidWatch site at http://www.jpl.nasa.gov/asteroidwatch/.
I’ve heard NASA has observed Elenin many times more than other comets. Is this true, and is NASA playing this comet down?
NASA regularly detects, tracks and characterizes asteroids and comets passing relatively close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them and predicts their paths to determine if any could be potentially hazardous to our planet. For more information, visit the NASA-JPL Near Earth objects site at http://neo.jpl.nasa.gov/ .
However, neither NASA nor JPL is in the business of actively observing Elenin or any other comet. Most of the posted observations are made by amateur astronomers around the world. Since Elenin has had so much publicity, it naturally has attracted more observers.
I was looking at the orbital diagram of Comet Elenin on the JPL website, and I was wondering why the orbit shows some angles when zooming? If you pick any other comet, you can see that there are no angles or bends.
Many people are trying to plot the orbit of the comet with the routine on the JPL website, without realizing that this is just a simple visualization tool. While the tool has been recently improved to show smoother trajectories near the sun, it is not a scientific program to generate an accurate orbit. Yeomans explains that the orbit plotter on the Near-Earth Object website is not meant to accurately depict the true motion of objects over long time intervals, nor is it accurate during close planetary encounters. For more accurate long-term plotting, Yeomans suggests using the JPL Horizons system instead: http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=C/2010%20X1 .
As many of our readers know, I also work with the 365 Days of Astronomy podcast. This award winning daily podcast that was supposed to last for only one year — the International Year of Astronomy — is now in its third year. Unfortunately, the 365 Days of Astronomy podcast is in trouble due to a lack of funding and audio. We’ve done over two and a half years — 959 podcasts so far — all on a shoestring and by the generous donations of audio and funds by our listeners. But things are looking a little grim, and we’d at least like to make it to the end of the year. As Pamela Gay said in her blog post about this, “At a certain level, it is hard to walk away from something feeling like it is halfway done. This is the 365 Days of Astronomy podcast, and we’d like to complete the 2011 calendar year.”
Each 365 Days of Astronomy podcast gets at least 3,000 downloads — some get as many as 10- 15,000 downloads. It’s a wonderful way to have your voice heard, your story told. As Phil Plait has mentioned, 365 DoA is a great venue to not only educate people about astronomy, but to get them personally involved. If you would, please consider submitting audio or making a donation to help us keep a good thing going. We know times are tough, but will appreciate any help you can provide.
This view of Earth comes from NASA's Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite. Image credit: NASA
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When it comes to planet Earth, it’s very important to know if we’re growing or shrinking. While plate tectonics are responsible for major changes in our planet’s outer crust, we need to have accurate measurements of our atmosphere and magnetic fields, too. To make these appraisals accurate, the global science community established the International Terrestrial Reference Frame.
At one time scientists theorized that Earth might be expanding or contracting. After all, major events like volcanoes, landslides and ice sheets were at the root of significant elevation changes. Even sizable climate events like El Nino and La Nina are responsible for redistributing large amounts of water. Now a new NASA study, published recently in Geophysical Research Letter, has pointed towards the utilization of space measurement tools and a new data calculation techniques which show no vital changes in the size of our planet.
Why is monitoring our size so important? The International Terrestrial Reference Frame is not only important for ground navigation, but satellite tracking as well. NASA says to think of it this way: “If all of Earth’s GPS stations were located in Norway, their data would indicate that Earth is growing, because high-latitude countries like Norway are still rising in elevation in response to the removal of the weight of Ice Age ice sheets.” So for all intents and purposes, the ITRF uses the average center of mass of the total Earth, a computation of a quarter of a century of satellite data. High-precision space geodesy includes:
Satellite Laser Ranging — a global observation station network that measures, with millimeter-level precision, the time it takes for ultrashort pulses of light to travel from the ground stations to satellites specially equipped with retroreflectors and back again.
Very-Long Baseline Interferometry — a radio astronomy technology that combines observations of an object made simultaneously by many telescopes to simulate a telescope as big as the maximum distance between the telescopes.
Global Positioning System — the U.S.-built space-based global navigation system that provides users around the world with precise location and time information.
Doppler Orbitography and Radiopositioning Integrated by Satellite — a French satellite system used to determine satellite orbits and positioning. Beacons on the ground emit radio signals that are received by satellites. The movement of the satellites causes a frequency shift of the signal that can be observed to determine ground positions and other information.
A team of scientists led by Xiaoping Wu of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and including participants from the Institut Geographique National, Champs-sur-Marne in France, and Delft University of Technology in The Netherlands are currently busy assessing the accuracy of the International Terrestrial Reference Frame. Through the use of the new data and calculation techniques combined with measurements of Earth’s gravity from NASA’s Gravity Recovery and Climate Experiment (GRACE) spacecraft and models of ocean bottom pressure, they are even able to account for minute changes in Earth’s gravity. The resultant changes have shown Earth’s radius to vary about 0.004 inches (0.1 millimeters) – or less than the thickness of a human hair.
“Our study provides an independent confirmation that the solid Earth is not getting larger at present, within current measurement uncertainties,” said Wu.
