Podcaster: Morgan Rehnberg
Title: Monthly News Roundup – Locations for Life
Description: In this episode of the Monthly News Roundup, the components and habitats for life are everywhere. From clouds of interstellar gas to the surface of Mars and the oceans of Europa, we explore places that might make like possible in the Universe. China launches an exciting new rover and Gaia sets out to map the Milky Way.
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.
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You’re listening to the 365 Days of Astronomy podcast for December 31st, 2013. I’m Morgan Rehnberg, here with Vivienne Baldassare, and this is the Monthly News Roundup. This episode was produced by Cosmic Chatter in Boulder, Colorado.
We start this month with drama on the ISS. You might think that the International Space Station, which orbits nearly four hundred kilometers above the Earth, would be a pretty cold place. After all, space is cold, right? It turns out that the answer is yes, and no. Space is indeed cold, but the ISS is in more danger of overheating than freezing. That’s because all the machinery and computers needed to keep people alive in space generate a lot of heat. The station actually has a heavy duty cooling system, part of which failed earlier this month.
The ISS is cooled by circulating tubes of ammonia around the station. Like your car radiator, the ammonia absorbs heat and moves it away from the source. It’s then cycled to two large cooling surfaces, which expose the lines to the coldness of space, removing the heat. It’s one of these that units failed. Since the ISS is built to be highly redundant, the lives of the astronauts aboard were never in immediate danger. One unit, however, is not enough to cool the laboratory under normal operations, so nonessential equipment had to be powered down. This included all the scientific experiments being carried out.
This actually isn’t the first time the cooling system has failed. The very same unit also needed repair back in 2010. When in space, however, no repair is easy. It required a series of long spacewalks in the days leading up to Christmas. Even these didn’t go off as planned. A spacesuit which almost drowned an astronaut back in July suffered yet another malfunction. This further delayed the repair effort, but by Christmas day the station was back to normal operation.
Events like this underscore the continuing courage of those willing to live and work in space. We’ve all had our share of air conditioning or heat troubles, but probably never have they placed us in danger or required personal risk to fix. No human has ever died in space, but that doesn’t mean the men and women who explore it aren’t constantly putting their lives on the line to bring us back the fantastical experiences we marvel at today.
NASA’s Curiosity Rover got us excited this month with its discovery of evidence for an ancient freshwater lake on Mars. This evidence comes in the form of mudstones found by Curiosity while roaming Gale Crater. Mudstones commonly form in still water as small particles of clay are deposited. Curiosity also found elements like nitrogen, hydrogen, and oxygen which are important for sustaining life. These mudstones could have supported chemolithoautotrophs, a form of microbial life that draws energy by breaking down minerals. These microbes are found on Earth, usually in places far below the Earth’s surface. They are essential for maintaining life on Earth, as they release nutrients from rocks and help form soil.
The minerals in the mudstone indicate the lake was most likely freshwater, and that the water was possibly even suitable for human consumption. This discovery further substantiates the claim that Mars was previously capable of supporting primordial life. The first evidence for this was found in March when Curiosity analyzed the chemical composition of a rock to find elements that are integral for supporting life as we know it.
With the discovery that freshwater likely once flowed on the Martian surface, we’ve come almost full circle. After all, it was only about a hundred years ago that Percival Lowell claimed to see canals on the surface of Mars. In the following decades, however, our notion of the planet’s surface couldn’t have been bleaker. When Mariner 4 returned the first-ever close-up images of the Martian surface, it revealed a starkly dry landscape. This picture was only further reinforced in the 1970s by the Viking landers. In fact, it wasn’t until the 21st century that we really found any concrete proof of a wet Mars.
Now that proof seems to be everywhere. From Spirit and Opportunity to Mars Reconnaissance Orbiter to Phoenix Mars Lander, it’s almost the norm now for missions to find evidence of water past and present. While it will never be Lowell’s vision of a dying civilization’s desperate attempt to save their home, the evidence we find opens up the possibility that humans can one day use the martian landscape to support ourselves.
In an alternate look at life in the cosmos, phosphorus, one of the six elements essential for life, has been found in the remnants of a supernova. This gives us the first observational confirmation that it is created by processes that occur during the lives of stars. It was discovered in supernova remnant Cassiopeia A, which consists of the gas left over from the fatal explosion of a massive star over three hundred years ago. Phosphorus has been identified in supernova remnants before, but astronomers were never able to confirm that it existed in larger quantities there than in the space between stars. However, in this study, they were able to confirm that the ratio of phosphorus to iron in Cassiopeia A is 100 times that found in the galaxy in general.
Most elements in the Universe are created by processes in stars. The only exceptions are hydrogen, helium, and lithium, which were created in the aftermath of the Big Bang. Stars fuse hydrogen into helium over the course of their lifetimes. When they run out of hydrogen, stars proceed on different paths depending on how massive they are. Low-mass stars like our Sun will be able to fuse helium into a few other elements, while heavy stars will go through several rounds of expansion and collapse that allow it to obtain the pressure and temperatures necessary to fuse elements up to and including iron. All elements heavier than iron must be created in violent supernovae explosions.
Phosphorus is special because it is found in our DNA, RNA, and cell membranes. The other elements essential for life are hydrogen, carbon, nitrogen, oxygen, and sulfur, all having been found in stars in abundance. This discovery gives us the first observations to confirm that phosphorus comes from processes inside stars as well. Though the lives and deaths of stars seem removed from life on Earth, it is these processes that enriched the Universe with the elements necessary for life to flourish.
For the first time in nearly forty years, we’ve successfully landed on the Moon. On December 14th, China became just the third nation in history to land a spacecraft on the lunar surface. The rover, named Jade Rabbit, represents a major step forward for the Chinese space program. Similar in size and capability to NASA’s Spirit and Opportunity rovers, Jade Rabbit will spend the next several months roaming the surface of the Moon. It’s already returned stunning pictures from the lunar surface, reminiscent of those taken by the Apollo astronauts.
But, in addition to its scientific endeavors, Jade Rabbit has another purpose: lunar prospecting. China is hoping to survey the rover’s landing site for minerals useful here on Earth. A number of elements and compounds which are rare here on Earth are relatively common in space. With the right price and high enough abundances, it may become economically viable to mine and return certain minerals to Earth. Helium-3, for example, has long been suggested as a viable fuel for nuclear fusion. It’s very rare on the Earth, but quite common in the lunar surface.
China is far from the only one looking to mine in outer space. A number of companies are in the early stages of developing the technology to mine near-Earth asteroids. While it’s likely to become economically viable, questions remain about the ethics and equality of space mining. We’ve only begun to study and understand the Moon. Is it appropriate, then, to begin strip mining it? And how do we divide it up? Is the next space race going to better resemble a gold rush than a scientific exploration? What about the countries without a space program of their own? Space mining has the possibility to return fabulous wealth, which could dramatically expand the gap between the haves and have-nots around the world.
These first steps, however, are exciting. As new countries join the effort to explore space, we can get more done more quickly and better bring the benefits back to the people of Earth.
The European Space Agency’s Gaia spacecraft had a successful launch earlier this month, and should begin taking observations soon. Gaia’s five year mission is to measure the distances and motions of one billion stars in the Milky Way, helping us to create the most precise three dimensional map of our galaxy ever.
How can it measure the distances to a billion stars in just five years? Gaia, like Hipparcos before it, uses the principle of parallax. Parallax is actually really easy to demonstrate for yourself. Hold your thumb out at arm’s length. Look at it through one eye and then the other. Notice how it moves back and forth? That’s the effect of parallax, and the distance side-to-side that your thumb appears to move can be used to compute the length of your arm. By observing stars at two different points in its orbit, Gaia does basically the same thing. But since stars are very far away, they appear to only shift by a tiny amount. Thus, very precise measurements are needed. Gaia will make these observations over 1000 times as precisely as Hipparcos.
Aside from measuring the distances to stars, Gaia will make contributions to numerous other subfields of astronomy. Since Gaia will observe each star up to seventy times, it will give us valuable information about how specific stars change with time. This sort of information is great for studying variable stars, or stars that have periodic fluctuations in their brightness. Gaia also has the capability to find lots of hypervelocity stars, or stars that are moving at speeds of up to 1000 kilometers per second, more than ten times faster than the average star. They are thought to get accelerated to these extreme speeds when binary star systems interact with the supermassive black hole at the center of the Milky Way. One star is captured by the black hole; the other is shot away with an extremely high velocity. To date, fewer than 20 of these hypervelocity stars have been identified. Since Gaia measures stellar motions of many stars to extreme precision, we will hopefully discover many more. Gaia may also detect new planets. Through its repeated measurements of the brightnesses of stars, it can detect the characteristic dip in the light from a star when a planet passes in front of it. It can also use its motion measurements to detect the wobble in the position of a star due to its planets tugging on it.
Though space missions are often designed with particular science goals in mind, Gaia is one example of the ways in which instruments created with a certain focus can also have wide-reaching applications. Gaia will also likely make discoveries that we cannot begin to anticipate.
In the search for life in the Universe, Jupiter’s moon Europa has always held a special place. Stanley Kubrick immortalized it with the line “All these worlds belong to you, except Europa. Attempt no landing there.” Since then, we’re found increasing evidence that the moon may be the sort of place life could survive. It is heated enough by tidal forces to sustain a liquid water ocean underneath its surface. And material blasted off Io by its volcanoes could land on Europa and foster the organic chemistry that underlies all life on Earth. But, because of ten kilometers of surface ice, we’ve never gotten a look at this watery world.
That all changed in December, when astronomers using the Hubble Space Telescope announced the detection of a giant plume of water emanating from the surface of Europa. Extending more than 200 kilometers above the surface, this feature looks similar to the water jet on Enceladus.
Such an extraordinary discovery will require more observations to confirm. But, if it proves to be real, a geyser could change the whole game when it comes to studying Europa. For years many have advocated for a mission to land on the surface, similar to what we’ve done on Mars. This is an expensive proposition, however, and we lack even moderate resolution maps of the surface from which to select a landing site. With a plume, we can put off the whole issue of landing to a later time. A Europa orbiter could fly through the plume and analyze its components while simultaneously developing the surface maps needed for a proper landing. In this way, we could have cheaper, more immediate results while still planning for the future.
If nothing else, this discovery casts doubt on NASA’s planetary exploration agenda. We’re spending billions of dollars to rove the surface of Mars to look for evidence of water from billions of years ago. Meanwhile, we’re spending very little time studying the sources of water actually present in the solar system today.
Thanks for listening to this episode of the Monthly News Roundup. For more astronomy news and commentary, visit http://cosmicchatter.org or follow @cosmic_chatter on Twitter. As always, you can send you comments and corrections to email@example.com. Have a happy new year!
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365 Days of Astronomy
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