Archive for the ‘space’ Category
Voyager into the void
The first human interstellar craft was launched in 1977. For the last 35 years it has been travelling inside a bubble of the sun’s atmosphere. NASA issued a press release claiming that Voyager 1 is now in interstellar space:
NASA’s Voyager 1 spacecraft officially is the first human-made object to venture into interstellar space. The 36-year-old probe is about 12 billion miles (19 billion kilometers) from our sun.
New and unexpected data indicate Voyager 1 has been traveling for about one year through plasma, or ionized gas, present in the space between stars. Voyager is in a transitional region immediately outside the solar bubble, where some effects from our sun are still evident. A report on the analysis of this new data, an effort led by Don Gurnett and the plasma wave science team at the University of Iowa, Iowa City, is published in Thursday’s edition of the journal Science.
“Now that we have new, key data, we believe this is mankind’s historic leap into interstellar space,” said Ed Stone, Voyager project scientist based at the California Institute of Technology, Pasadena. “The Voyager team needed time to analyze those observations and make sense of them. But we can now answer the question we’ve all been asking — ‘Are we there yet?’ Yes, we are.”
A separate press release from NASA explains how they conclude that the craft has reached interstellar space:
Whether and when NASA’s Voyager 1 spacecraft, humankind’s most distant object, broke through to interstellar space, the space between stars, has been a thorny issue. For the last year, claims have surfaced every few months that Voyager 1 has “left our solar system.” Why has the Voyager team held off from saying the craft reached interstellar space until now?
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In May 2012, the number of galactic cosmic rays made its first significant jump, while some of the inside particles made their first significant dip. The pace of change quickened dramatically on July 28, 2012. After five days, the intensities returned to what they had been. This was the first taste of a new region, and at the time Voyager scientists thought the spacecraft might have briefly touched the edge of interstellar space.
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By Aug. 25, when, as we now know, Voyager 1 entered this new region for good, all the lower-energy particles from inside zipped away. Some inside particles dropped by more than a factor of 1,000 compared to 2004. The levels of galactic cosmic rays jumped to the highest of the entire mission. These would be the expected changes if Voyager 1 had crossed the heliopause, which is the boundary between the heliosphere and interstellar space. However, subsequent analysis of the magnetic field data revealed that even though the magnetic field strength jumped by 60 percent at the boundary, the direction changed less than 2 degrees. This suggested that Voyager 1 had not left the solar magnetic field and had only entered a new region, still inside our solar bubble, that had been depleted of inside particles.
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Then on April 9, 2013, it happened: Voyager 1’s plasma wave instrument picked up local plasma oscillations. Scientists think they probably stemmed from a burst of solar activity from a year before, a burst that has become known as the St. Patrick’s Day Solar Storms. The oscillations increased in pitch through May 22 and indicated that Voyager was moving into an increasingly dense region of plasma. This plasma had the signatures of interstellar plasma, with a density more than 40 times that observed by Voyager 2 in the heliosheath. [Listen to these plasma oscillations]Gurnett and Kurth began going through the recent data and found a fainter, lower-frequency set of oscillations from Oct. 23 to Nov. 27, 2012. When they extrapolated back, they deduced that Voyager had first encountered this dense interstellar plasma in August 2012, consistent with the sharp boundaries in the charged particle and magnetic field data on August 25.
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“What we can say is Voyager 1 is bathed in matter from other stars,” Stone said. “What we can’t say is what exact discoveries await Voyager’s continued journey. No one was able to predict all of the details that Voyager 1 has seen. So we expect more surprises.”Voyager 1, which is working with a finite power supply, has enough electrical power to keep operating the fields and particles science instruments through at least 2020, which will mark 43 years of continual operation. At that point, mission managers will have to start turning off these instruments one by one to conserve power, with the last one turning off around 2025.
Voyager 1 will continue sending engineering data for a few more years after the last science instrument is turned off, but after that it will be sailing on as a silent ambassador. In about 40,000 years, it will be closer to the star AC +79 3888 than our own sun. (AC +79 3888 is traveling toward us faster than we are traveling towards it, so while Alpha Centauri is the next closest star now, it won’t be in 40,000 years.) And for the rest of time, Voyager 1 will continue orbiting around the heart of the Milky Way galaxy, with our sun but a tiny point of light among many.
A romance of the martian atmosphere
Two papers published together in Science, one by Webster and friends, the other by Mahaffy and friends, find something exciting about the early history of Mars. Apparently, the Martian atmosphere started out similar to the Earth’s, but some catastrophic event about 4 billion years ago stripped Mars of its air and water.
How does data collected by the Curiosity rover on Mars tell us so much? A nice explanation is given in a podcast on Science. Here is a summary from the transcript:
Interviewer – Linda Poon
Okay. And from my understanding, the lighter isotope escapes, and that’s how you guys are using that as evidence of Mars atmospheric loss?Interviewee – Christopher Webster
Yes, that’s exactly right. If you look at carbon, for example, most of carbon has a mass of 12, but one in every 100 atoms has a mass of 13. This is an isotope of carbon. So in carbon dioxide, there’s a small amount of carbon dioxide that’s carbon-13. And it should be in the normal ratio like we find on Earth, but on Mars, we see because, as you said the lower mass escapes more easily, we see this enrichment, if you like, in the heavier carbon-13. [Our new measurements] tell us they’re in the proportion that we see in the meteorites. And that’s very important because we believe that certain meteorites are from Mars.Interviewer – Linda Poon
And then you also measured the deuterium-to-hydrogen ratio, and you found evidence for
two-stage evolution for martian water. Can you tell us a little about both the measurement and these two stages?Interviewee – Christopher Webster
[The] deuterium-to-hydrogen ratio, [is] a simple measurement for identifying the origin of planets and the evolution of the solar system. It tells us where Earth’s water came from. It’s believed to have come from cometary and asteroid input or delivery, if you like, of water to Earth. And all that story is wrapped up in this D/H ratio that we look at of many planets. On Mars, it’s a special case, because the escape removes the lighter hydrogen. You’re left with a heavier deuterium, so it’s very high in its D/H ratio. Our results support the idea of the significant, early loss a long time ago and then a small loss over the last three to four billion years. We looked at the D/H; we saw very high values. And then we’re now looking at that same ratio in the dust and the rocks of Mars, and we’re seeing very different values in those. So again, we have this tremendous capability to tie the history of water on Mars. We know it had a watery past. Now we can map out how that water evolved with time and was lost and how it interacts with the atmosphere in the escape process.
Alien skies
T. M. Evans of the University of Oxford and nine others used the Hubble Space Telescope to make an observation which is now published in Astrophysical Journal Letters, and claims:
We present a secondary eclipse observation for the hot Jupiter HD189733b across the wavelength range 290–570nm made using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We measure geometric albedos of Ag=0.40±0.12 at 290–450nm and Ag<0.12 at 450–570nm. The albedo decrease towards longer wavelengths is also apparent when using six wavelength bins over the same wavelength range. This can be interpreted as evidence for optically thick reflective clouds on the dayside hemisphere, with sodium absorption suppressing the scattered light signal beyond ~450nm as predicted by models of hot Jupiter atmospheres. Our best-fit albedo values imply that HD189733b would appear a deep blue color at visible wavelengths.
The Guardian translates this into:
Astronomers used the ageing Hubble space telescope to determine the true colour of the distant world, the first time such a feat has been achieved for a planet that circles a star other than the sun.
Unlike the pale blue dot that harbours all known life in the cosmos, the “deep blue dot” is an inhospitable gas giant that lies 63 light years from Earth. On HD189733b, as the planet is named, the temperature soars to 1,000C and glassy hail whips through the air on hypersonic winds.
Though the planet is hostile to life as we know it, the same technique could be used to spot potentially habitable worlds, through changes in cloud cover and other features.
Frederic Pont at Exeter University observed the planet before, during, and after it passed behind its star. When the planet was on either side, the telescope collected light from the star along with light reflected from the planet’s surface. But as the planet moved behind the star, the light it reflected was blocked out.
Using an instrument onboard the telescope called an imaging spectrograph, Pont noticed that blue light dimmed sharply as the planet passed behind its star, but brightened again when it emerged on the other side. “As far as I am aware, nobody has had actual results on the colour of an exoplanet,” Pont said. “Now we can say that this planet is blue.”
Largest storm in the solar system
A press release from NASA explained:
NASA’s Cassini spacecraft has tracked the aftermath of a rare massive storm on Saturn. Data reveal record-setting disturbances in the planet’s upper atmosphere long after the visible signs of the storm abated, in addition to an indication the storm was more forceful than scientists previously thought.
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First detected by Cassini in Saturn’s northern hemisphere on Dec. 5, 2010, the storm grew so large that an equivalent storm on Earth would blanket most of North America from north to south and wrap around our planet many times. This type of giant disturbance on Saturn typically occurs every 30 Earth years, or once every Saturn year.Not only was this the first storm of its kind to be studied by a spacecraft in orbit around the planet, but it was the first to be observed at thermal infrared wavelengths. Infrared data from CIRS allowed scientists to take the temperature of Saturn’s atmosphere and to track phenomena that are invisible to the naked eye.
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Temperature measurements by CIRS, first published in May 2011, revealed two unusual beacons of warmer-than-normal air shining brightly in the stratosphere. These indicated a massive release of energy into the atmosphere. After the visible signs of the storm started to fade, CIRS data revealed the two beacons had merged. The temperature of this combined air mass shot up to more than minus 64 degrees Fahrenheit (above 220 kelvins).According to Hesman, the huge spike of ethylene generated at the same time peaked with 100 times more ethylene than scientists thought possible for Saturn.
An earlier video also recorded the sounds of lightning in the storm.
Two ways to make the moon
The composition of the moon and the earth are so similar that most planetologists now beleive that the moon must have formed from ejection of material from the earth. This is thought to be caused by the collision of a different planet with the proto-earth. Many problems arise in this scenario. This week there are two possible detailed answers to how the moon was made.
Science published a paper by Robin Canup from the University of Boulder, Colorado which says:
In the giant impact theory, the Moon forms from debris ejected into an Earth-orbiting disk by the collision of a large planet with the early Earth. Prior impact simulations predict that much of the disk material originates from the impacting planet. However, the Earth and Moon have essentially identical oxygen isotope compositions. This has been a challenge for the impact theory, because the impactor’s composition would have likely differed from that of the Earth. Here, we simulate impacts involving larger impactors than previously considered. We show that these can produce a disk with the same composition as the planet’s mantle, consistent with Earth-Moon compositional similarities. Such impacts require subsequent removal of angular momentum from the Earth-Moon system through a resonance with the Sun, as recently proposed.
The figure on the right shows that after the initial impact, the planets re-collided, merged, and spun rapidly. Their iron cores migrated to the center, while the merged structure developed a bar-type mode and spiral arms (24). The arms wrapped up and finally dispersed to form a disk containing about 3 lunar masses whose silicate composition differed from that of the final planet by less than 1%.
Back-to-back with this in Science is an article by Matija Cuk and Sarah Stewart of Harvard University, Massachusetts, which claims:
A common origin for the Moon and Earth is required by their identical isotopic composition. However, simulations of the current giant impact hypothesis for Moon formation find that most lunar material originated from the impactor, which should have had a different isotopic signature. Previous Moon-formation studies assumed that the angular momentum after the impact was similar to the present day; however, Earth-mass planets are expected to have higher spin rates at the end of accretion. Here, we show that typical last giant impacts onto a fast-spinning proto-Earth can produce a Moon-forming disk derived primarily from Earth’s mantle. Furthermore, we find that a faster-spinning early Earth-Moon system can lose angular momentum and reach the present state through an orbital resonance between the Sun and Moon.
This figure shows an example of an impact of a light planet with a proto-Earth spinning with a period of 2.3 hours. The colors denote the silicate mantles and iron cores of the Earth and impactor. The disk is dominated by material originating from Earth’s mantle near the impact site. After material is ejected from the earth, it condenses into a moon. The high speed of rotation (technically, angular momentum) is transferred to the sun through a mechanism known as an orbital resonance.
The main difference between the two mechanisms is that the first requires a very large mass impactor, whereas the second can make do with a light impactor.
Neil Armstrong 1930-2012
Businesweek records the life of Neil Armstrong, the first man on the moon:
Armstrong was born Aug. 5, 1930, on a farm near Wapakoneta in western Ohio. He took his first airplane ride at age 6 and developed a fascination with aviation that prompted him to build model airplanes and conduct experiments in a homemade wind tunnel.
As a boy, he worked at a pharmacy and took flying lessons. He was licensed to fly at 16, before he got his driver’s license.
Armstrong enrolled in Purdue University to study aeronautical engineering but was called to duty with the U.S. Navy in 1949 and flew 78 combat missions in Korea.
After the war, Armstrong finished his degree from Purdue and later earned a master’s degree in aerospace engineering from the University of Southern California. He became a test pilot with what evolved into the National Aeronautics and Space Administration, flying more than 200 kinds of aircraft from gliders to jets.
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He commanded the historic landing of the Apollo 11 spacecraft on the moon July 20, 1969, capping the most daring of the 20th century’s scientific expeditions and becoming the first man to walk on the moon.His first words after the feat are etched in history books and the memories of the spellbound millions who heard them in a live broadcast.
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An estimated 600 million people — a fifth of the world’s population — watched and listened to the landing, the largest audience for any single event in history.
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Armstrong, who had bypass surgery earlier this month, died Saturday at age 82 from what his family said were complications of heart procedures. His family didn’t say where he died; he had lived in suburban Cincinnati.He was “a reluctant American hero who always believed he was just doing his job,” his family said in a statement.
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“I am, and ever will be, a white socks, pocket protector, nerdy engineer,” he said in 2000 in one of his rare public appearances. “And I take a substantial amount of pride in the accomplishments of my profession.”Rice University historian Douglas Brinkley, who interviewed Armstrong for NASA’s oral history project, said Armstrong fit every requirement the space agency needed for the first man to walk on moon, especially because of his engineering skills and the way he handled celebrity by shunning it.
“I think his genius was in his reclusiveness,” said Brinkley. “He was the ultimate hero in an era of corruptible men.”
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For anyone else who wanted to remember him, his family’s statement made a simple request:“Honor his example of service, accomplishment and modesty, and the next time you walk outside on a clear night and see the moon smiling down at you, think of Neil Armstrong and give him a wink.”
USA Today reported a wonderful tribute from John Glenn:
On a personal note, Glenn spoke of the lessons from Armstrong’s life.
“It would be great if every person could find something like that that would give them that much pleasure that they would dedicate their lives to. Everyone should pick their field they are interested in and then try to get the finest education possible to allow them to participate in that field.”
Xinhua reported:
Regardless of his feat in accomplishing the most daring scientific expedition of the 20th century, Armstrong remained modest and self-effacing.
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“I guess we all like to be recognized not for one piece of fireworks but for the ledger of our daily work,” he said in a CBS interview.Armstrong left NASA a year after the Apollo 11 mission to become a professor of engineering at the University of Cincinnati.
The Guardian recalled Armstrong’s last interview:
He described the crew’s harrowing 12-minute descent to the moon, when he realised that the Eagle lunar module’s auto-pilot was preparing to land the crew on the slope of a huge moon crater. “The computer showed us where it intended to land, and it was a very bad location, on the side of a large crater about 100-150m in diameter with very steep slopes covered with very large boulders – not a good place to land at all,” he said.
Armstrong took over the craft manually and managed to land it like a helicopter in a smoother area to the west with just 20 seconds of fuel left.
As for “that’s one small step for [a] man, one giant leap for mankind,” Armstrong says he didn’t think of those words until after they’d landed safely.
Of his time on the moon’s surface, he said: “It was special and memorable but it was only instantaneous because there was work to do. We weren’t there to meditate. We were there to get things done. So we got on with it.”
In Washington Post, a lovely story from a press conference in 1999:
The thing that everyone has asked them for 30 years is how the trip to the moon changed their lives, and this day was no exception. It’s a question they struggle with. Aldrin, always the most garrulous, came closest to answering, mentioning his evolving spirituality. On the moon, he served himself communion, which seemed appropriate at the time. Since then, he said, he’s adopted a more “Einsteinian” view of the universe, what he called a “cosmic religious” sensibility.
Armstrong said that, because of the moon trip, “I get to go to a lot more press conferences” at which people ask how the moon changed his life.
He then said he didn’t know how it had changed his life because, having been to the moon, he had no way of knowing what his life would have been like had he not gone to the moon. This was vintage Armstrong: Logic rules.
And yet he also had the most purely inspiring comment of the day. When he was a kid, the same age as the students asking questions, no one had ever flown a plane at supersonic speed. There was no space program. Going to the moon was pure science fiction. In his lifetime–in the first half of his lifetime–everything changed.
“Opportunities will be available to you that you cannot imagine,” he said.
So true. So very true.
I was among the half billion of humankind who followed the chatter of the Eagle’s descent from orbit to the moon, by radio, because there was no TV in India then. Most childhood heroes fall by the way, because their achievements do not grow as you do. By going back to a life, and managing that re-entry well, by continuing to do his job, Neil Armstrong remained a hero.
Self portrait by Curiosity
More information and images available at the web home of NASA’s mars Curiosity rover
Moon map
More Intelligent Life reports on NASA’s new map of the moon:
the multinational team behind this image first designed a new Wide Angled Camera (WAC) capable of withstanding the vicissitudes of outer space. They then hitched a lift for it on a spacecraft: the Lunar Reconnaissance Orbiter (LRO), which was launched by NASA in 2009 and has already gone beyond its initial mission to spend a year in close orbit of the Moon. The palm-sized WAC was mounted on the LRO, which flies at an average altitude of 50km (30 miles) above the Moon’s surface. Each picture it takes covers a swathe 70km wide.
As the LRO is constantly circumnavigating the Moon, with each orbit 30km (in ground distance) from the last, the pictures it takes overlap, giving a stereo view of almost every patch of lunar ground, every month. About 69,000 of these images were sent back and fed into a computer, which used them to build an accurate model of almost all the terrain. The bits at extreme latitudes that the WAC couldn’t survey—the holes at the poles—were covered by another laser instrument on board, known as LOLA (Lunar Orbiter Laser Altimeter).
But it was only when the models were shaded, to give a sense of the relief, and coloured in with different altitudes shown by different colours, that the topography was transformed into a living landscape—of craters, mountains and the vast basalt plains that early astronomers mistook for seas and lakes. “I could not be more pleased with the quality of the map,” said Mark Robinson, who heads the Arizona team. “It’s phenomenal. The richness of detail should inspire lunar geologists around the world for years to come.”
Karela Fry 