The science and environment news highlights of 2013
It was the year in which an object from the cosmos burned and boomed its way through our atmosphere while one originating on Earth hurtled into the uncharted territory of interstellar space.
BBC News website science editor Paul Rincon looks back at a memorable year of science and environment headlines. And you can view a picture gallery of the highlights here.Fire in the sky
On 15 February, skywatchers were gearing up for the close flyby of Earth by a large asteroid. But on the day of that pass, a different 10,000-tonne space rock burned up over Chelyabinsk, Russia, injuring more than 1,000 people as its shockwave shattered glass and rocked buildings.
This spectacular "cosmic coincidence" gave scientists an unprecedented opportunity to study the anatomy of an asteroid strike, in part thanks to the dashboard cameras - dashcams - installed by Russian drivers to combat insurance scams and police corruption. The largest chunk of the meteorite was later retrieved from the bottom of Lake Chebarkul.
In March, scientists had outlined their results showing that Nasa's Voyager-1 spacecraft had left the heliosphere - the bubble of hot gas from our Sun - in August 2012. But officials from the space agency quickly countered the claims.
Voyager's epic journey
By September, the outlook had changed, and mission scientists published their own evidence - incorporating additional data - confirming the probe's entry into the region between stars.
Though a handful remain doubtful, Voyager-1 - launched in 1977 to study the outer planets - appears to be the first manmade object to reach interstellar space.Dangerous download
In May, BBC News broke the story of the world's first 3D printed gun being successfully fired in the US. A controversial group tested the weapon at a firing range near Austin, Texas. Designer Cody Wilson, who described himself as a crypto-anarchist, said he was "seeing a world where technology says you can pretty much be able to have whatever you want".
The blueprint used to produce the plastic gun had been downloaded about 100,000 times in just under a week after it went online. The US government later demanded that blueprints for the firearm be removed from the web, amid criticism from anti-gun campaigners.Watch the skies
One advance in physics this year has the potential to spawn a new branch of astronomy. In May, the BBC News website was first to report that the IceCube experiment, buried in the ice at the south pole, had seen high-energy neutrino particles streaming in from outside our Solar System.
While existing branches of astronomy make use of different wavelengths of light, such as optical or infrared, this development makes it possible to picture the cosmos using particles. And there were delights for cosmologists, as a spectacular map of the oldest light was assembled from data gathered by the Planck telescope.Cull or cure?
The coalition government began its controversial pilot badger culls in Gloucestershire and Somerset in 2013. Ministers had set the target of killing 70% of badgers in the cull zones over six-week periods to reduce the incidence of TB in cattle. But companies charged with culling the animals fell short of the mark.
Official documents seen by the BBC showed that government agency Natural England doubted the Gloucestershire cull would reach the 70% target even with an extension - a prediction that would later be borne out. However, ministers defended their strategy, arguing that the more badgers were removed, the greater the benefits to cattle.Tough climate
In September, a UN panel of experts released its long-awaited report detailing the physical evidence behind climate change. The scientists working with the Intergovernmental Panel on Climate Change (IPCC) said they were 95% certain that humans had been the "dominant cause" of global warming since the 1950s.
Despite this, and projections suggesting 2013 could be among the warmest years on record, the political process to reduce emissions remained precarious. And the warming "pause" continued to stump climate scientists, with the ban on CFC gases and natural cooling in part of the Pacific ocean among the reasons proposed.Nanotubes and 'spooky action'
A team of scientists at Stanford University unveiled the first computer made of carbon nanotubes in September. The device, known as "Cedric", is only a basic prototype but could be developed into a new generation of digital devices that are smaller, faster and more efficient that today's silicon models.
In another development, Nasa and Google agreed to share a $15m computer that reportedly uses quantum physics effects to boost its speed. The D-Wave machine had drawn scepticism from researchers in quantum computing until a scientific paper in April suggested it was indeed exploiting the strange behaviour of matter at quantum scales. However, the exact mechanism remains opaque.
D-Wave's computer isn't the only thing tapping successfully into the quantum world; bird migration and the mechanics of smell were targets for research in the nascent field of quantum biology.Unlocking the past
In 2013, tests revealed that human remains estimated to be 4,000 years old and found at County Laois, Ireland, could represent the oldest bog body yet. Yet the chemistry which pickles bodies in bogs does not favour the preservation of DNA, which is unfortunate given the potential information these bodies could give up.
This year saw the oldest human DNA sequence described as well as the most complete genome sequence from a Neanderthal. These studies revealed unexpected links between human groups, evidence for inbreeding and interbreeding, and the presence of a mystery early human species. But ancient DNA can also be put to use solving more recent puzzles about human migrations.Future fuels
The UK chancellor George Osborne committed his support to companies involved in shale gas "fracking", which has had a dramatic effect on the energy sector across the pond. So much so, that in 2013, the US began exporting shale gas for the first time. But fracking is but one of a variety of technologies designed to extract difficult-to-reach hydrocarbon deposits.
But energy analysts will also have been closely monitoring the rapid transition to renewables in Germany. Despite huge opportunity, questions remain over who pays, the effects on tourism and the feed-in tariffs that could make renewable energy too expensive to store.Forest menace
Ecologists continued to monitor the threats facing Europe's forests, including the ash dieback which has now arrived in Britain. In 2013, it emerged that another menace had arrived on the continent: the emerald ash borer. Forest fragmentation can have dramatic effects on the species that rely on these habitats for survival, a study in Science journal also showed this year.Discovery and de-extinction
Amid the sixth great mass extinction of life on Earth, researchers continue to find biological species previously unknown to science. This year's stand-out discovery was the olinguito (pictured above), a mammal living in the cloud forests of Colombia and Ecuador.
Whilst no antidote to the biodiversity crisis, scientific advances might make the revival of extinct species possible. While many dream of seeing ancient giants such as the woolly mammoth walk the Earth again, more recently extinct species - such as the gastric brooding frog and the bucardo - are better candidates in the near term.Mind mapping
A US-led venture to map the wiring of the human brain released its first results in March. The Human Connectome Project should help determine how a person's brain structure affects their abilities and behaviour. The BBC's Pallab Ghosh got to test out the group's cutting edge imaging techniques on his own brain.
The BBC also reported that efforts were underway to understand the workings of the teenage brain, to identify changes to the brain's wiring that controls impulsive and emotional behaviour as young people mature. One astonishing addition to the neurological bonanza was the news that scientists in Japan had been able to use MRI scans to "read" the images people saw in their dreams.New space pioneers
A nascent "space race" heated up in 2013, as India launched an unmanned probe towards Mars and China successfully landed its Jade Rabbit rover on the Moon - the first "soft" landing on the lunar surface in 37 years.
How to put a human on Mars
Meanwhile, scientists at Imperial College London collaborated with the BBC to show how they would mount a manned voyage to Mars. Crewed missions to the Red Planet were all the rage in 2013: Space tourist Dennis Tito announced his search for a mature couple to undertake the journey, while the team behind the Mars One mission stated plainly that applicants for the venture would be on a one-way ticket.Jean genie
No, we didn't forget. Canada's social-media friendly space station commander Chris Hadfield cemented his internet stardom when he handed over command of the outpost, popped a protein pill and hammered out a very competent rendition of David Bowie's Space Oddity from Earth orbit in what had been dubbed the "first music video in space". You can view the zero-g original here, and an Earth-gravity version below.