Tag: Space

• What Your Fruit Bowl and the Galaxy Have in Common

  August 26, 2018 4:50 pm Comments Off on What Your Fruit Bowl and the Galaxy Have in Common

  Antimatter is one of the ultimate science-fiction ideas: matter with the incredible destructive power to ‘annihilate’ when it comes into contact with ordinary matter. In Dan Brown’s ‘Angels and Demons’, the idea of a destructive antimatter bomb is a key plot point. Despite what science fiction would have you believe, the scientific fact of antimatter is much more benign. In fact, you may have a common antimatter source lurking in your fruit bowl right now!
  When scientists talk about the production of antimatter, it usually brings to mind particle accelerators – like the Large Hadron Collider at CERN – which are capable of producing vast amounts of antiparticles by colliding extremely energetic particles. However, some everyday items are actually tiny antimatter factories that don’t require such superconducting magnets. One form of radioactivity, beta decay, can produce anti-electrons or positrons. A radioactive element that decays to produce positrons is Potassium-40. A potassium-rich fruit, like that banana sitting in your fruit bowl, can contain up to 48 micrograms of radioactive potassium and will thus produce a positron every 75 minutes or so.  
  Should you be worried about your daily banana? The level of radiation produced by an average banana (known by scientists as the ’banana equivalent dose’) is a measure of the level of radiation exposure encountered on a daily basis. To put it simply, it isn’t harmful. In fact, eating a banana a day exposes you to substantially less radiation than what you would experience taking a plane ride from Canberra to Sydney. You would have to eat 200 bananas to be exposed to a comparable amount of radiation from a chest x-ray, and it would take around 100 million bananas to kill you (and the cause of death probably wouldn’t be radiation sickness)! The antimatter itself shouldn’t worry you either: the positron produced inside the banana will encounter an electron almost instantly, annihilating the positron before it can escape.
  However, the story would be very different in space. Suppose you take all the radioactive potassium atoms and put them into orbit around the Earth. Space is a near-vacuum – there is around one atom per cubic centimetre, making it far less likely for a positron produced by radioactive atoms to bump into a rogue electron and annihilate. This means that positrons can float around for millions of years, carried on magnetic currents in interstellar space before they extinguish. The idea of radioactive material in space isn’t fanciful either. When dying stars form elements, they are often created in highly radioactive states which later decay. Many of these decays can produce positrons, which then float around for a while before eventually annihilating.
  So, is there antimatter annihilating with electrons out in space? For fifty years, astronomers have observed antimatter positrons via the high energy radiation produced by this process. The exact origin of these positrons has been uncertain for most of that time. However, a small team of researchers, including several astronomers from ANU, think they may have found the answer. They have concluded that a rare type of dying star system may be responsible.  
  Unlike the sun, some stars are born in pairs, known as ‘binary star systems’. Once they run out of fuel to produce heat and light, all that remains of these deficient mass binary systems is a pair of ‘white dwarf stars’. If a white dwarf star forms on its own, it will eventually cool and fade. However, in a binary system, two white dwarf stars can spiral closer and closer together until they merge, causing a supernova explosion. This explosion produces large quantities of radioactive material.
  Last year, in a paper published by ANU astronomer Dr Roland Crocker and his collaborators, the astronomers described how this process can form radioactive titanium, which decays to produce positrons. Even if only one of these supernovae occurs in our galaxy every few hundred years, they can generate almost 10^42 positrons per second, explaining the origin of most of this galactic antimatter.
  What also makes these supernovae special, is that they occur among five billion-year-old stars, whereas ordinary supernova explosions are usually associated with stars less than a billion years old. Hence, scientists mapping the annihilation of positrons find that most positrons annihilate where the oldest stars in our galaxy are, not in regions where one would expect to see ordinary, run-of-the-mill dying stars. This offers a crucial piece of the puzzle of understanding the origin of galactic positrons.
  So next time you look at your fruit bowl, you can remind yourself that your banana and our galaxy have something in common that sounds more like science fiction than fact: they’re both excellent sources of antimatter. Just keep your banana away from Dan Brown’s Illuminati.

  Fiona Panther

• The Moon: A ‘Gas Station’

  August 12, 2018 9:49 am Comments Off on The Moon: A ‘Gas Station’

  In February this year, US Commerce Secretary Wilbur Ross announced the Trump administration’s intention to commercialise our galaxy and discussed turning the Moon into a ‘gas station for outer space’.
  Is this even possible? Could the Moon be a place where future spacecrafts refuel?
   
  The Science Behind It
  As Secretary Ross pointed out, below the surface of the Moon lie ‘hundreds of feet of solid ice’. The plan to convert this ice into fuel involves breaking the ice down into hydrogen and oxygen and using them as a ‘propellant’. Scientifically, he’s not wrong. Burning hydrogen as fuel after it has been separated from water through electrolysis is a common procedure in space exploration today. You probably even did an experiment demonstrating this principle when you were in high school!
  What’s amazing about this process is that when burning hydrogen rather than traditional petrol or gas, harmful pollutants or greenhouse gases are not emitted. Instead, the hydrogen reacts with the oxygen in the air to form water, making it a clean and renewable energy source. Furthermore, as the gravitational attraction on the Moon is much less than that experienced on Earth, less fuel would be needed to launch a spacecraft into outer space from its surface.
  So, the science checks out. Using the Moon as a cosmic gas station would save a lot of money when it comes to space travel and pave the way for the greater commercialisation of space. What’s holding us back then?
   
  The Policy Behind It
  Whilst Secretary Ross covers the science pretty well, he’s still missing a few key points. For one, the Moon Agreement of 1979 outlines that no state can claim sovereignty over the Moon. This exists alongside the International Space Station Intergovernmental Agreement of 1998, which says that any space station positioned on the Moon can be accessed by any country. These agreements aren’t exactly conducive to fostering an environment that the private sector can commercialise.
  And there is the issue of Space Law. We’ve already seen what happens when there are space accidents involving multiple parties. In 1978, the USSR’s nuclear powered Kosmos 954 satellite crash-landed in Canada. Even though the Soviet Union was ‘responsible’, there were no laws telling them they were ‘liable’ –  meaning they weren’t legally required to pay Canada a cent of compensation. What would this mean if there was a potential large-scale disaster on the Moon? Countries and companies could use this loophole as a way of escaping their legal responsibilities on Earth.
  Insurance companies could help this situation, as private insurance for outer space already exists. However, with science pushing the boundaries of what is capable for space exploration, such companies are becoming increasingly hesitant to insure against a growing number of uncertain possibilities and potential accidents in space.  
   
  Looking Ahead
  So, will the Moon become a ‘gas station’ for outer space? I don’t have the answers to this question, and quite frankly, neither does the UN. It’s been argued by many that we’ll simply ‘cross that bridge when we get to it’. But with the US’ ambitions to expand their dominance in space through private sector commercialisation – which is indeed the most cost-efficient way of developing space technology – the right legal frameworks are first needed to help with the commercialisation process. What will come first, the chicken or the egg?
   

  Woroni SubEditor

• Life on Mars?

  9:32 am Comments Off on Life on Mars?

  “On Earth, where there’s water, there’s life. Could be we’re not alone.” – Chris Hadfield, CSA & NASA
  For thousands of years, humans have gazed at the stars and dreamed of the possibilities that lie beyond this small, blue planet which we call home. From down here, the sheer enormity of space can be difficult to grasp. The Earth orbits the sun, which spins in a galaxy alongside another 250 billion suns. Further beyond still, our Milky Way Galaxy is merely one of an approximated 100 billion other galaxies. Either we are alone in this enormous universe, or somewhere out in the vast, all-encompassing darkness, there exist other lifeforms surviving in environments completely different to our own. The question as to whether we are alone in the universe remains contentious, but perhaps the answer to this search could be much closer to home than expected?
  On Wednesday the 25th of July, Science Magazine published evidence of a vast liquid-water lake located beneath the south pole of Mars. This ground-breaking discovery comes after decades of investigation into the conditions of our planetary neighbour and has led some to believe that life on Mars, either past or present, is a real possibility.
  Could life have once thrived on this desolate and barren wasteland? If networks of liquid water do exist below the freezing surface, could microbial life still survive and thrive there to this very day? Perhaps it is possible that we are not alone in our own Solar System…
  Let’s take a look at what we know so far.
  Timeline of Mars Discoveries:
  1972: Images from NASA space probe Mariner 9 reveals dry river beds and canyons on the surface of Mars, as well as evidence of water erosion, weather fronts and fogs. This was the first evidence of water on Mars.
  1978: The Viking program returns images to Earth of geological formations on Mars’ surface, typically formed by large amounts of water. These include rivers, valleys and dams.
  1997: The Mars Pathfinder mission observes rock formations consistent with strong flood waters in the past. This mission also reports evidence of clouds and maybe fog.
  2003: Technology on board the Mars Odyssey detects vast quantities of ice water under the surface of Mars.
  2003: Trace amounts of methane discovered in Mars’ atmosphere introduces the possibility of microorganisms inhabiting the planet.
  2006: Photos of two craters on Mars are released, pointing to the possibility of liquid water existing on the planet.
  2007: The Spirit rover uncovers a layer of Martian soil containing evidence of a past hot spring environment, which would have been ideal for microbial life.
  2008: The presence of water ice on Mars, detected by the Mars Odyssey mission, is confirmed by the Phoenix lander.
  2010: The Mars Reconnaissance Orbiter reports strong evidence for sustained precipitation and locates many ideal sites to investigate for evidence of life.
  2018: A 20km wide liquid lake is detected under the south pole, buried under 1.5km of mantle.
  So, do these discoveries point towards the existence of life on Mars? That’s the thing: we have no idea. Theoretically, if the liquid lake is found to be a part of a larger network of underground reservoirs, microbial life could be discovered under the surface of Mars. Microbial life can survive and thrive in environments which are generally considered extreme and inhospitable, so there is a chance that if Mars was once teeming with microorganisms, life may still be present. It is important to remember that despite this exciting discovery, there is currently no solid evidence to confirm this theory. Years more research is required to even come close to determining whether life existed, or still exists, on Mars.  
  Watch this space.  

  Sophie Burgess