Naked Science Question and Answer

Scientists in Helsinki have spotted an asteroid behaving badly, and it's all down to light. Mikko Kaasalainen, from the University of Helsinki in Finland, has been watching an asteroid called Apollo, which is about 1 mile across and spinning. But careful measurements have revealed that the asteroid is very slowly altering its rotational period, by about one 4000th of a second every year. It's the result of a phenomenon called the YORP effect, short for Yarkovsky-O'Keefe-Radzievskii-Paddack effect. This occurs when light hits a surface and gives it a push. But because the asteroid is an irregular shape some parts of it receive a bigger push when sunlight hits it than other parts. The result is that the object's rotational period begins to change. So could this push an asteroid into the path of the Earth, provoking a collision? "Theoretically yes," says Kaasalainen, "but the reverse is also true and scientists have suggested making part of the surface of an Earth-bound asteroid more reflective to take advantage of this effect and avoid a collision". The observations are published in this week's Nature.

Researchers are getting ready to test a tobacco-powered aeroplane thanks to a new bio jet fuel made from the seeds of nicotine-free plants, and the result could be a 75 % reduction in carbon emissions compared to fossil fuels.

Dr Sergio Tommasini has a dream: fields of tobacco as far as the eye can see, thousands of hectares of green stretching across South Africa, Brazil and Europe.

But he is not some latter-day pedlar of a cancer-causing weed. In fact, if you smoke one of his leaves you'll likely spit it out in disgust, says Dr Tommasini, managing director of Sunchem Holding, an Italian research and development company.

For this tobacco has no nicotine. It is grown for its seeds, which are rich in oil that can be used to make bio jet fuel.

And a tobacco-powered Boeing plane will be roaring along the Cape Town-Johannesburg corridor conducting tests within months, if things go to plan.

'It's going to be the greenest flight ever,' said Dr Tommasini.

Launched in December 2014, Project Solaris is a collaboration between his company, the sustainable jet fuel supplier SkyNRG, and some private investors, supported by South African Airways and the aerospace company Boeing. The EU has part-funded their feasibility study to test the viability of the process before it is scaled up.

The hybrid tobacco, Solaris, for which Sunchem holds the international patent, currently grows on 50 hectares of land in Limpopo province, in the northeast of South Africa. Some two to three tonnes of crude oil can be pressed from its seeds per hectare per year, says Dr Tommasini.

Solaris has been bred to have leaves much smaller than the flappy ones of a normal tobacco plant, and to have oily seeds. The scientists believe it can overcome the notorious troubles that arose around first-generation biofuels such as sugar cane and maize, accused of competing with food production.

In South Africa, at least, it won't be food-versus-fuel, but fuel-versus-smokes - and Solaris could also be used in rotation on the 70 000 hectares of cotton plantations in the country, says Dr Tommasini.

Elsewhere, such as in Europe, it could be rotated with food crops, which would enhance the soil and break disease cycles. Meanwhile, the leftovers from seed-pressing yield a rich animal feed.

'It's not toxic, so it is feeding into the nutrition cycle,' he added.

Aviation

So, is tobacco the answer to the dreams of the aviation industry?

In 2015, Solaris became certified by the Roundtable on Sustainable Biomaterials (RSB), a global scheme supported by the World Wide Fund for Nature (WWF), supporting the sustainable production of biofuels and other biomaterials.

Over the lifecycle of the fuel, it will lead to a cut of 75 % in carbon emissions compared with its fossil fuel counterparts, says Dr Tommasini -- much better than the threshold of a 50 % reduction set by the RSB.

But Dr Jeremy Woods from the Centre for Environmental Policy at Imperial College London, UK, who is not involved in the project, says that, however hard they try, such lifecycle calculations can't fully take into account the carbon cost that comes with the clearing of virgin land for cultivation - which can happen indirectly because the original crop has been displaced to some other, previously unplanted terrain.

He recently calculated that four million hectares of land would need to be deployed to biofuel crops in order to supply the aviation industry.

"On the one hand it's very unlikely that biofuels could service today's and the future aviation industry," says Dr Woods. But a more nuanced goal, in which biofuels are a partial and intermediate solution, looks more feasible.

"If you see biofuels as a share of a transition programme, then it suddenly doesn't look impossible," he says.

Tree tobacco

Head north-east from South Africa and you'll hit the island of Madagascar, where scientists are growing a single hectare of the toxic, invasive tobacco tree, Nicotiana glauca -- known for its love of the driest, hottest, most inhospitable patches of our crowded planet - which they want to turn into a source of sustainable energy and materials.

Tree tobacco is a mostly unwelcome addition to a nation's flora. It is indigenous to South America, and is smoked by some Native Americans, but it is tenacious and invasive in many parts of the world. Victims of its poisonous leaves include some people who have mistaken it for spinach, and a number of ostriches.

But lately scientists have grown excited about its extraordinary ability to do without groundwater and its apparently low demand for other essentials such as the nitrogen required for photosynthesis.

"It's an incredibly hardy species and the growth is really quite astounding," says Dr Alisdair Fernie, of the Max Planck Institute of Molecular Plant Physiology in Potsdam, Germany, who coordinates the MultiBioPro project, an industry-academic partnership funded by the EU.

This is a plant that does not need pampering with micro-irrigation, a common technique when farming in very dry soil. Instead it appears to absorb moisture from the air through its pores.

"As a potential biofuel this is essentially gold dust," says Dr Fernie. "It grows not even on marginal land but land that is completely bankrupt for agricultural use."

Work on N. glauca is less advanced than on Solaris. Field trials have been done in the United Arab Emirates, and the hectare under cultivation in Madagascar will soon be harvested and the seeds taken to Germany for an attempt at biorefining for jet fuel, or as an additive to other fuels to reduce their emission of particulates and carbon monoxide.

As with Solaris, finding multiple uses for every part of the plant is thought to be key to its success, so MultiBioPro is also considering how the tree's biomass can be processed into other products.

Within the toxic leaves lurks Vitamin D - a product increasingly in demand as a supplement - and these also contain solanesol, widely used in the pharmaceutical industry. Another strand of research in the programme is looking at other chemicals it might produce...

Chelsea - Since 1955 America has spent 35 billion dollars on Polio vaccination, that might seem like a lot but that spending has generated a net saving of over 180 billion dollars, that's according to a new analysis by scientists at the Harvard School of Public Health. Lead author Kimberly Thompson says they modelled how the disease would have spread without vaccinations and then estimated how much it would have cost to treat it.

Kimberly - People often don't realise that its hard to get credit for things that don't happen. This is a real challenge because with respect to public health because if people don't see the benefits of intervention but they look at the cost, then they might misperceive in fact how very valuable public health interventions are.

Chelsea - She says that's an important lesson not only for efforts to eradicate Polio in developing countries, but also for healthcare systems in developed countries where emergency treatment often trumps preventative care.

Bob - A new kind of drug may fight viruses and other causes of disease by silencing their genes. The key ingredient is small interfering RNA, a molecule that can block specific genes from making proteins. Julie Leberman from Harvard Medical School says such drugs would have broad potential.

Julie - Since the machinery for RNA interference exists in all cells, this natural pathway can be used to silence any gene that might be involved in disease.

Bob - In animal studies, Leberman's team found a way to get interfering RNA into infected cells without affecting healthy cells. Now she and her colleagues are working RNA therapies for a respiratory virus, pandemic 'flu and even high cholesterol.

Chelsea - Thanks Bob, next time we'll look at how global warming could break up some happy symbiotic relationships. Back to you Naked Scientists...

When you actually have a meteor or an asteroid hitting the Earth it doesn't create a nuclear reaction its literally just the energy from the speed that it hits. If you drop a stone off the Empire State building it will probably hit the floor at a few metres per second, when an asteroid comes in and hits the Earth its probably coming in at maybe 20km per second. Incredibly fast - what we call hyper-velocity, and literally that energy from such a massive object, it could be hundreds of metres or even kilometres across, hitting something and basically stopping dead - all that energy from the speed it was going at gets immediately converted into heat or sound waves propagating through the crust of the Earth. It can do immense damage to the Earth and basically blast vast amounts of rock and debris up into the atmosphere which can cause climate change and all sorts of nasty problems.

What happens with an eclipse with the moon is the Earth passes exactly between sun and the moon, so basically the Earth's shadow is cast on the surface of the moon. Which is why you get that dark colour going across the surface, its sort of a reddish colour basically because you're getting a little bit of light filtering round the edge of the Earth through the atmosphere. The atmosphere lets red light get through better than blue light so you get a reddish tinge to the moon. Other things do get eclipsed, with the sun that's when the moon passes exactly between the Earth and the sun. Actually the day before the lunar eclipse we had an occultation of Saturn, where are moon passed exactly between us and Saturn. So Saturn disappeared out of view, you get the same affect from stars and other planets. They can be really useful things to watch; you can find out about the atmospheres of other planets by watching the stars vanish behind them.

It's a really good way to detect a planet around another sun. As the planet passes in front of that other star it blocks out a little bit of the light and it goes slightly dimmer for perhaps a few hours and we can actually see that from the Earth sometimes and actually work out that there's another planet orbiting around another star somewhere.