Podcaster: Morgan Rehnberg
Title: Monthly News Roundup – Staying in the Solar System
Link : http://cosmicchatter.org
http://cosmicchatter.org/news/2014/4/23/astronauts-repair-iss-with-speedy-spacewalk
http://www.jpl.nasa.gov/news/news.php?release=2014-112
http://blogs.discovermagazine.com/d-brief/2014/04/18/mountains-on-saturns-moon-iapetus-fell-from-the-sky/#.U1rYFdywLYg
http://cosmicchatter.org/news/2014/4/25/spacex-successfully-lands-rocket-will-sue-us
http://cosmicchatter.org/?tag=Cosmos
Description: In this episode of the Monthly News Roundup, astronauts repair the ISS with a speedy spacewalk. Saturn is full of moon news and SpaceX takes a big step towards a new future for spaceflight. Cosmos continues to impress.
Bio: Morgan Rehnberg is a graduate student in astrophysics and planetary science at the University of Colorado – Boulder. When not studying the rings of Saturn, he develops software to help search for asteroids that might hit the Earth. He blogs and podcasts about astronomy and space science at http://cosmicchatter.org.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by — no one. We still need sponsors for many days in 2014, so please consider sponsoring a day or two. Just click on the “Donate” button on the lower left side of this webpage, or contact us at signup@365daysofastronomy.org.
Transcript:
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You’re listening to the 365 Days of Astronomy podcast for April 29th, 2014. I’m Morgan Rehnberg and this is the Monthly News Roundup. This episode was produced April 25th from Boulder, Colorado.
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Our top story this month is an emergency spacewalk aboard the International Space Station. Orbiting more than four hundred kilometers above the Earth’s surface, the ISS must provide orbiting astronauts with everything they need to live and work in space. Few things are more important than a functioning communication system and so when tests on April 11th revealed that a backup communications computer was malfunctioning, mission controllers knew they needed a fix.
The computer in question was called MDM-2. MDM stands for Multiplexor/Demultiplexor. Multiplexing is a method of combining many signals into a single one that can make much more efficient use of a given communications frequency. To support control of all the station’s equipment, the ISS has several tiers of MDMs which pass commands around the laboratory.
Although this was never a life-threatening glitch, the computer needed to be repaired. The trouble is, MDM-2 is the only ISS computer located outside the station. This meant that a spacewalk would be necessary, something that NASA has been taking pains to avoid since last year’s troubles with malfunctioning suit heaters and drinking systems.
Just days before the planned extra-vehicular activity, or EVA, SpaceX’s Dragon capsule delivered a new spacesuit and some parts to aid in the repair and on April 22 astronauts conducted the shortest-ever successful ISS spacewalk to make the repair. NInety minutes after leaving the station, they were sealing the airlock behind them once more.
With MDM-2 functioning once more, full redundancy has been returned to the lab’s systems and life can go on as normal. Or at least as normal as an astronaut’s life can be…
http://cosmicchatter.org/news/2014/4/23/astronauts-repair-iss-with-speedy-spacewalk
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Let’s head out to the Saturn system to take a look at the possible birth of a brand new moon. A group of astronomers, led by Britain’s Carl Murray, announced this month that their analysis of images from the Cassini spacecraft may have revealed a new moon embedded within the rings.
The Saturn system is already chock full of moons, with more than 60 observed at last count. Many scientists believe that many of these may have originated within the rings. One popular hypothesis suggests that the disintegration of a large, Titan-sized moon may have formed the rings. Those rings would have been far more massive than the ones we observe today. This extra material clumped together to form many of the small and medium-sized moons seen today. Gravitational interactions with the ring would cause these bodies to migrate outward to their current positions.
The authors of this study suggest that this new object, nicknamed Peggy, could be the last remnant of this process. It’s too small for even Cassini to see directly, meaning that it probably has a size no larger than half a kilometer. Will it escape the rings? That’s a tricky question. Peggy is currently trapped at the edge of the A ring, which lies within a boundary called the Roche radius. Inside of this line, the gravity of Saturn is strong enough to disrupt objects that aren’t entirely solid. Some features in the Cassini images suggest that this could be happening.
If Peggy is indeed destroyed, it will only be the next step in the life cycle of Saturn’s rings. The material ripped off of the moon will stir up the surrounding area, lead to new collisions, and begin the process of forming the next moon. Life, death, and life again is the story of the rings.
http://www.jpl.nasa.gov/news/news.php?release=2014-112
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If we drift out just a little farther in the Saturn system, we come upon another remarkable moon: Iapetus. Named after a Titan of Greek mythology, Iapetus is Saturn’s third largest moon and perhaps its strangest. Noting that he could only see Iapetus half as frequently as he expected, seventeenth-century astronomer Giovanni Cassini himself deduced that the moon must have an enormous color dichotomy. In fact, one side of the moon is more than ten times more reflective than the other.
Perhaps even more striking, though, are observations made by Cassini the spacecraft. It discovered a circumlunar ridge: basically a range of mountains running entirely around the equator of Iapetus. Calling it a ridge is actually rather misleading: these peaks are taller than Mount Everest!
How this remarkable feature formed has long been a question of great interest to astronomers and planetary scientists. This month, a group of researchers suggested an answer.
Their hypothesis is based off of one of the more unusual features of these mountains: their slope. Physics tells us that you can only pile material up so steeply before it begins to tumble down and the ridge of Iapetus is quite near this limit. On the Earth, plate tectonics can sometimes overcome such limits, but Iapetus likely never had such activity. And other ways of creating mountains, like volcanism, produce features that are much less steep.
From this, the scientists concluded that the material must have fallen from space. How could this have happened? They propose an impact between Iapetus and another body produced a large ring of material in orbit about the moon. Over time, material from this ring fell back onto the surface, landing preferentially on the equator. When this material built up, it became the equatorial bulge we see today.
A similar effect could have occurred on the Earth during the formation of our moon, but subsequent geologic activity has erased all traces of this process. This leaves Iapetus as the sole ridged body we’ve ever discovered!
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When a SpaceX Falcon 9 rocket lifted off earlier this month to boost a supply-laden Dragon capsule to the International Space Station, it cost about $60 million. Seems like a lot, right? That’s actually far cheaper than other ways of getting payloads into space. But what if it could be even cheaper? That’s the promise of reusable rockets.
When the Falcon 9 launches, only about one third of one percent of its cost is the fuel needed to power the engine. That’s less than $200,000 dollars. The other 99% of the cost goes into the materials and labor to build the rocket itself. At the end of the flight, all that effort plunges into the ocean, lost forever. But, does it have to be?
SpaceX has set out to answer that with a resounding “no,” and this month they took a major step towards the goal of reusable rockets. After boosting the Dragon capsule to the ISS, this time the Falcon 9 extended landing legs and restarted its engine. This brought it to a hover just above the surface of the ocean, demonstrating for the first time that a rocket in full flight could return, under control, to the Earth.
It wasn’t the whole rocket that returned under control, but the part that did makes up about 70% of the Falcon 9’s cost, so even if more couldn’t return, we’re still talking about a major savings.
SpaceX plans several more ocean landings before they attempt to return a Falcon 9 to land by the end of the year. At that point, engineers will be able to inspect the used rocket and determine what would be required to fly it again.
It’s hard to overstate how important reusable rockets could be. The more durable a product is, the more effort we can put into improving and advancing it. Imagine if a jet airliner was destroyed after every flight. It probably wouldn’t be full of bathrooms and TVs and windows if that were the case. We’ve never before gotten there with a rocket, so it’s anyone’s guess where this might lead us, but one thing’s for sure: it’s going to lower the bar for entry into space.
http://cosmicchatter.org/news/2014/4/25/spacex-successfully-lands-rocket-will-sue-us
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Finally, April provided another month of excellent episodes from the reincarnated Cosmos with Neil deGrasse Tyson. The show continues to display a variety that perhaps many of us didn’t expect, with episodes this month ranging from the nature of light to lead as a public health menace.
It’s clear that Tyson, writer Ann Druyan, and others on the show hold the same perspective on science as Carl Sagan did: that the Universe is not solely what we see when we look up at the night sky. In Sagan’s words:
“The Cosmos is all that is or was or ever will be. Our feeblest contemplations of the Cosmos stir us — there is a tingling in the spine, a catch in the voice, a faint sensation, as if a distant memory, of falling from a height. We know we are approaching the greatest of mysteries.”
Science isn’t just an awe of the stars and planets and galaxies out there in the Universe. It’s an awe of ourselves: of the molecules that form our bodies, of the chemistry that animates us, of the wondrous discoveries we have labored to uncover.
This new series is clearly vividly cognizant of this awe, but equally aware that revelations of this magnitude are not always the easiest to accept. With a sure hand and a gentle tone, it’s leading a whole new generation of viewers to a new perspective on their lives and the reality of the world around them. I sure can’t wait for another month of this!
http://cosmicchatter.org/?tag=Cosmos
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Thanks for listening to this episode of the Monthly News Roundup. For more astronomy news and commentary, visit http://cosmicchatter.org or follow us at @cosmic_chatter on Twitter. As always, we welcome your comments and corrections at cosmicchatter@gmail.com. See you in May!
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365 Days of Astronomy
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