The year 2018 provided plenty to chew on if you're interested in science and the environment. From the stark warning from climate scientists about the dangers of letting temperatures rise beyond 1.5C to the discovery of a 20km-wide liquid water lake on Mars, it was a memorable year.
Here's a rundown of some of 2018's most eye-catching stories.
A "safe" limit for warming
A rise in global temperatures of 2C by the end of this century has long been seen as the gateway to dangerous climate change. Researchers had argued that keeping within this limit was necessary to avoid the most damaging effects of global warming.
But some have been pushing for an even lower target of 1.5C. In October, climate scientists released a major report detailing what would be involved in keeping the temperature rise to within that tougher limit.
This would result in millions fewer people losing their homes to rising seas, fewer species at risk of extinction and a drastic reduction in the numbers of people experiencing water scarcity.
But it would also be hugely expensive and require "rapid, far-reaching and unprecedented changes" to society. The report didn't tell governments what to do, but set out a range of approaches including heavy cuts in greenhouse gas emissions, a rapid transition to renewable energy and lifestyle and dietary changes.
Other climate change stories from 2018
The earliest animals
The one-million-plus animal species alive today are staggeringly diverse, from the giant oceanic blue whale to the wriggly earthworms beneath our feet. But their early evolution from single-celled ancestors remains shrouded in mystery.
In the hunt for the earliest animal life, much attention has been focused on a group of enigmatic life forms – known as the "Ediacaran biota" – from more than 500 million years ago. These were some of the first complex organisms to appear on Earth.
But their position on the tree of life is difficult decipher. These curious creatures have been variously categorised as lichens, fungi, and even as a halfway house between plants and animals.
In September, scientists were able to extract molecules of cholesterol from a fossilised Ediacaran life form called Dickinsonia, which resembled a flat jellyfish. Cholesterol is one of the molecular hallmarks of animal life, clearly demonstrating that the Ediacaran biota were animals.
Other palaeontology stories from 2018
Giant plastic 'berg
The world's plastic waste crisis was one of the big themes of 2018. The problem had been highlighted by the BBC's Blue Planet 2 series, presented by David Attenborough, which contained shocking footage of the devastation wrought on the oceans and marine life by our addiction to plastic.
In April, our Science Editor, David Shukman, visited Indonesia to report on a morass of plastic waste that had clogged rivers and canals in Bandung, on the Indonesian island of Java. The crisis was so acute, the army was called in to help clean up a vast plastic 'berg of bottles, bags and other plastic packaging.
Worryingly, the problem only looks set to get worse. In March, a report commissioned by the UK government suggested the amount of plastic in the ocean could triple in a decade unless litter is curbed.
Other plastic waste stories from 2018
Ghost particle busters
Neutrinos are some of the fundamental building blocks of the Universe. These sub-atomic particles hurtle around the cosmos more-or-less unimpeded, interacting with very little. In fact, it's estimated that a single neutrino particle can pass through a light-year (about 10 trillion km) of lead without hitting a single atom.
Many neutrinos we encounter on Earth come from the Sun or the Earth's atmosphere. But the origins of one group of ultra-high-energy neutrinos remained mysterious until this year. In July, an international team traced one of them to a distant galaxy firing a particle "ray" straight at the Earth.
This type of galaxy is called a blazar. It has an intensely bright core caused by the energy of its central, massive black hole. As matter falls into the hole, enormous jets of charged particles emerge, turning these galaxies into vast particle accelerators.
The IceCube experiment in Antarctica has been collecting data on these ultra-high-energy neutrinos for six years, but this was the first time researchers were able to match them with a source in the sky.
Other astronomy stories from 2018
A watery Mars – and Moon
We know there is water on Mars in the form of ice, and there are possible signs of occasional liquid flows. But in July, a team of scientists reported the discovery of a 20km-wide lake sitting under the planet's south polar ice cap.
Nasa's Curiosity rover has been exploring the rock remnants of an ancient lake bed, but this is the first sign of a persistent body of water today. The result was exciting because scientists have long hunted for signs of present-day liquid water on Mars.
"We are not closer to actually detecting life," said Manish Patel, from the UK's Open University, "but what this finding does is give us the location of where to look on Mars."
Mars wasn't the only cosmic body making watery headlines. In August, researchers published what they said was the most definitive evidence yet for ice on the surface of the Moon.
Data from India's Chandrayaan-1 spacecraft suggests the presence of icy deposits at the north and south poles. This ancient water might be accessible as a resource for future human missions to the Moon.
Other planetary science stories from 2018