Food science, ancient human genes, and dark comets

British scientists have created the world’s first carbon-14 diamond-based battery. By capturing the fast moving electrons given off when radioactive carbon-14 atoms decay, none of which can escape their hard diamond casing, the technology promises to provide power to devices at low levels for potentially thousands of years. Here’s the creator Tom Scott at the University of Bristol…

Tom - Instead of using nuclear fission, for example, which is what we do in a reactor to heat water to create steam and drive a turbine and in doing so generate electricity, we're actually generating electricity directly through radioactive decay. What we've developed effectively is a cousin to the solar panel, except instead of needing sunlight to generate the electricity from the panel, we're actually using radiation. What we're actually doing is embedding inside the voltaic the radioactive material such that the energy is produced and converted inside a single device. That makes it very efficient.

Chris - So what materials are you using and what's the origin of the radioactivity in the first instance?

Tom - Radioactivity that we've been using in this first device is an isotope of carbon called carbon 14. Actually, carbon 14 is naturally created in the upper atmosphere. The presence of it means that we can do things like carbonating archaeological finds, but in our case, because it's radioactive, when it decays it releases a beta particle, which we then convert into a trickle of electricity in our devices. Now, our devices are actually made from diamond, which is a phase of carbon, which is really very hard. It's actually one of the hardest natural substances on the planet. What we do is, we grow diamond from a gas plasma that we create, and we incorporate into the diamond the radioactive carbon. All we're doing is we're substituting non-radioactive carbon in the diamond for radioactive carbon. Because the diamond is really dense and it's really hard, it forms a really, really good cage. That means that we can convert the radiation energy into electricity, but also the radioactivity doesn't escape from the device, which makes it intrinsically safe.

Chris - You've got the radioactive source, which is the atoms of carbon 14 inside the diamond, what are they hitting in order to produce the electricity and then for you to tap off the electricity if that's all going on inside a diamond?

Tom - We create a special structure within the diamond. It's actually what we call a diode structure. That means that any electrons that we create within the device will flow in a single direction out of the device, which we can then connect to a working circuit. That might be a transmitter, it might be some sensors that we can make some readings with. A beta particle you can think of as being an extremely high energy electron. When that fires out into the diamond structure, you can think of it as bouncing its way through the structure and, with each collision it makes with another carbon atom, energy is dissipated into the structure of diamond as essentially like a cascade or a shower of electrons. It's that shower of electrons, which is the electricity, which is then flowing out of the device. I like to describe it as being something a bit like a sandwich. In our device we have a layer of diamond which is not radioactive, and then we have a layer which is radioactive, and then we have another layer which is not radioactive again, but it's been doped in order to help with the flow of the electrons in one direction out of the device. A bit like a ham sandwich where the ham layer is the bit for our diamonds, which is the radioactive bit.

Chris - How much energy comes out, at what sort of voltages, and how long will this last?

Tom - We're talking about devices which are never going to power cars or trains. We're talking about devices which constantly trickle out a tiny amount of power, and we’re talking microamps, at about two volts, but it would do so for a very long period of time. The half-life of carbon 14 is about 5,300 years. That means that with our devices they will have hit half power output over that period of time. In terms of human timescales, we're talking about a forever device, but in terms of geological timescales, we're talking about a device which would continue to produce power for several thousand years.

Chris - What do you think you can do with it? When you know you've got something at two volts with a few micro amps, what sort of things could that power?

Tom - Typically, we are looking at device applications where we can use that trickle of power, either because it's at sufficient level it can continually power a very low power consumption activity, that could be something like a pacemaker potentially, but for most of the device applications that we've already done a prototype for, we're trickle charging a very low leakage capacitor which is storing the electrical energy. When that capacitor over a period of time gets full, it then will discharge itself into a working circuit which might contain sensors or transmitters, for example. We see these devices as working in what we call a chirp mode. Every so often a device will chirp some information or it'll make a reading and then send that information and it will do that for very long periods of time. Potentially very useful in things like environmental monitoring in very extreme places where it's either very hot or very cold or maybe for example at the bottom of the sea or even at the bottom of an oil and gas well or where we're storing carbon dioxide, but also lots of applications in space where it can go from very hot to very cold quickly and you also need a device which can withstand the sort of solar radiation that's much stronger out beyond the protective bounds of the atmosphere. Really we're not looking to replace or supplant the standard lithium ion battery. What we're trying to do is provide a power source which is very good across extreme environments and also in very remote locations where it would be very expensive or potentially dangerous to try and go and replace a chemical battery.

In 2017, the first object we’ve been able to observe visiting our solar system from outer space tumbled into view. Because of its peculiar, cigar-like shape and was moving in an odd, extremely rapid way, it ignited a media frenzy with speculation that it might be an alien spaceship. Further investigation eventually concluded that it was indeed an alien insomuch as it was from somewhere outside our own solar system, but it was nevertheless a lump of rock, and somewhere between an asteroid and a comet. Space scientists named it ‘Oumuamua’, meaning ‘a messenger from afar’ in Hawaiian, a nod to where the telescope used to discover it was located. Now, scientists have documented seven more new so-called ‘dark comets’ which are not from outside the solar system but do still show strange patterns of movements. It comes in the same week a team from MIT have described 100 small asteroids (some just 10 metres in width) in our Solar System’s main belt using the James Webb Space Telescope. Here to make sense of it all for us is David Rothery, professor of planetary geosciences at the Open University…

David - There are asteroid like bodies which have been seen to move in trajectories which are not quite the orbits that they should have. The orbital path of anything around the sun is basically an ellipse if it's within the solar system. There are some slight perturbations to orbital motion because of how sunlight is reflected and absorbs heat, is reradiated, but we have about 14 objects which are being called dark comets, which is a bit of a misnomer, but you'll see why they're called comets. The explanation for these non gravitational accelerations or perturbations in the trajectory is that they must be degassing, and gasses are escaping and flinging away some dust, and the reaction against the dust being thrown away is what causes the main object speed and direction to change.

Chris - And did they come from our Solar System or outside the Solar System? Because the original claim when Oumuamua, the first one that was documented a few years ago now, was written about, people said this was an alien spacecraft because it appeared to be coming from outside the Solar System. How did they know that and where did the rest of them come from?

David - The object now known as Oumuamua was discovered when it was screaming through the Solar System at far too fast a speed to be orbiting the Sun. A few people said, "It's the alien spaceship from far reaches of our galaxy adjusting its trajectory with reaction rockets or something." But no, it's just small amounts of degassing. Something from very deep space is going to have ices in it, which when you get close to the sun, the ices will sublime, some dust will be thrown up, and the speed and direction of travel will be tweaked ever so slightly. Now the dark comets are not interstellar objects, they're orbiting the sun, about half of them are near Earth objects, their orbits come past the Earth, and others stay out in the main asteroid belt. They're not the same class of body as Oumuamua, but they've got the same phenomenon going on, which is material being thrown off in too small quantities for us to see, but which we can infer because of the way their orbital paths or orbital trajectories are being changed.

Chris - I'm slightly disappointed that they're not alien spacecraft, that would be quite intriguing and quite a discovery, wouldn't it, but one of the things that people do speculate in some of the coverage of this is, well these sorts of objects might be seeding life giving molecules. They're not themselves aliens, but they might bring life that can take root in various places. Is that overegging the pudding?

David - I think it is, Chris. To have volatiles, volatile substances and presumably some carbon rich material, that's the material which you need on a young planet for life to form. But these objects, they're fragments of larger things. This class of objects we've seen crossing the Earth were not there four and a half billion years ago when the Earth was forming. So it hasn't taught us really anything about the delivery of organic materials to the early Earth.

Chris - Talking of interesting things that are also out there and occasionally visit the earth, as in they come and produce fireballs and stuff, those are asteroids that come and rain in on our atmosphere from time to time. There's this other paper which is documenting enormous numbers of small asteroids, and is this right, that they can see something 10 metres across way beyond the orbit of Mars, from Earth? That's just outstanding astronomy.

David - Yeah, these are observations by the James Webb Space telescope or JWST. It has detected large numbers of what are being called decameter sized asteroids, that's 10 meters or a few tens of meters in size. There's a lot of 10 metre sized material out there, some of which will eventually get onto orbits which intersect with the Earth, but it doesn't mean they're a big threat to the Earth because objects of this size probably wouldn't get through the atmosphere intact.

Chris - What's the importance of the discovery, then? Or is this just the James Webb team flexing their astronomical muscles to show we can do this, this is why this is a powerful instrument. Look what sort of resolution we can achieve.

David - I think this is a wonderful bonus discovery. I'm not sure if this was in the plan for JWST. They wanted to look for planets around other stars. They wanted to do deep sky work and there are these wonderful images we see of all kinds of things in deep space. But it just shows that when you get a new wavelength accessible to you, in the infrared light of JWST with high resolution, no light pollution, no thermal pollution, you are able to do a lot, and the observations to discover this class of bodies and to get the statistics on them so they can learn about the dynamics of the collision and fragmentation process going on, this is all a bonus from staring at primary targets. It just shows that when you build a good instrument, you can do so many more things with it that perhaps you didn't expect.