These are Our Picks for the Top Science Stories of 2015

From Rosetta’s ongoing love affair with a comet and the discovery of a pentaquark, to controversial breakthroughs like gene-editing of human embryos and a possible new species of homo sapiens, these were the science stories everyone was talking about in 2015.

Rosetta and Its Potato-Shaped Comet

The European Space Agency’s Rosetta mission to explore Comet 67P/Churyumov-Gerasimenko was the science-y gift that kept on giving in 2015, particularly its slew of eye-popping images to delight space porn enthusiasts everywhere. It started in January with seven articles in Science describing the first findings from an analysis of the data: most notably, images of ripples and dunes on the comet’s surface. This was surprising because there is no atmosphere (and thus no wind) on the comet, plus it has very little gravity.

As the year progressed, we got stunning new photos from a low-altitude flyby, our first glimpse of the comet’s dark side, and new data from the Philae lander after it woke up from a months-long hibernation. There were plenty of surprises: for instance, the comet has a small weather system driven by an intense day-night cycle, complex organic molecules, and primordial oxygen leaking from what passes for the space rock’s tenuous atmosphere. And astronomers are still puzzled by the changing land features of one particular site on the comet. We can’t wait to see what Rosetta and its plucky potato-shaped comet have in store for us in 2016.

[Note: Pluto was also very big news in 2015—so much so that we’re giving everyone’s favorite dwarf planet a list all its own. Look for it this week.]

Illustration of a pentaquark particle. Credit: CERN.

The LHC Discovers a Pentaquark

The new improved Large Hadron Collider wasted no time getting down to business this year: its LHCb experiment promptly discovered a new class of subatomic particles dubbed “pentaquarks.” To make protons and neutrons, you bind three kinds of quarks together, but it is theoretically possible to make particles with as many as five quarks. The LHCb team found the signature of just such a beast, made up of two up quarks, one down quark, one charm quark, and one anticharm quark.

The first evidence for a possible pentaquark appeared in 2002 at the Spring-8 synchrotron in Harima, Japan, and initial re-analysis of the data strengthened the case. But by 2005, physicists had concluded it wasn’t a real signal, and for the last decade, the pentaquark has frequently been cited as an example of how easy it is to see something in the data that isn’t really there. Now we know the pentaquark actually exists, although the LHCb pentaquark is different from the one supposedly seen in 2002 (it’s three times heavier and contains different kinds of quarks). Still, it sets the scene for exciting new developments to come. As MIT’s Frank Wilczek, one of the architects of the theory that describes the forces holding quarks together, told Nature: “It’s like a phoenix rising from the ashes.”

Skeletal fossils of the hand of homo naledi. Credit: John Hawks/Wikimedia Commons

Possible New Species of Homo Sapiens

The excitement was palpable when researchers from University of the Witwatersrand in Johannesburg uncovered 15 partial skeletons deep in a South African cave system of what they believe to be an entirely new human-like species. Dubbed Homo naledi, the remains indicated that this creature had an ape-like pelvis and shoulders, with feet resembling that of homo sapiens 200,000 years ago, and a much smaller skull than modern humans. The team also uploaded digital copies to a site called Morphosource, so anyone could download them and print their own skull fragments with a 3D printer.

But the find proved controversial from the start, with other paleoanthropologists contending that it wasn’t really a new species, although they didn’t agree on which existing species it most closely resembles—and team member John Hawks posted a spirited rebuttal to the critiques on his blog, including access to his data. There have also been accusations that team leader Lee Berger rushed through the excavation and publication (apparently the paper was riddled with errors) to better accommodate a film crew for National Geographic. Whether or not those criticisms hold up, there’s no denying this was big news in 2015. And as Gizmodo’s own Kiona Smith-Strickland pointed out, “That’s the nuts and bolts of how scientific arguments are supposed to work.”

Credit: Wellcome Images.

Gene-Editing of Human Embryos

Following weeks of speculation, news broke earlier this year that Chinese geneticists had used the revolutionary new CRISPR gene-editing method to genetically modify the DNA of human embryos. Controversy immediately erupted, largely because of ethical questions surrounding their use of germline modification—unlike somatic gene therapies, germline modifications can be passed down to subsequent generations. The experiment wasn’t exactly a smashing success: they applied CRISPR to 86 embryos; 71 survived the process, and of those, 54 were genetically tested. Of those, only 28 spliced successfully, and only a fraction of those contained the replacement genetic material. There were also so many unintended mutations that the researchers opted to stop the experiment.

Frankly, the paper itself proved problematic: it was rejected by both Nature and Science, on ethical grounds, and ultimately published by Protein and Cell. But its broader impact was undeniable, motivating some of the world’s leading geneticists and bioethicists to convene an International Summit on Gene Editing several weeks ago. The subsequent report laid out some surprisingly forward-thinking guidelines: it gave U.S. scientists a green light on doing such experiments on human genes, provided those experiments don’t result in pregnancy. But the committee also cautioned against the prospect of “designer babies,” since the technology is still grossly premature.

One Step Closer to a Universal Flu Shot

Flu shots change with the seasons, because there are so many different strains; the shots must be tailored to whichever strains are dominant in any given year, based on the shapeshifting decoy proteins that line the virus’s surface. By putting those decoy proteins in our vaccines, we prime our immune systems against the flu. But now we’re one step closer to a universal flu shot—a single jab that could inoculate us for life—after two research groups announced new prototype vaccines that target a different, more stable “stalk protein” in the virus. The trick is to get our immune system to “recognize” those stalk proteins from year to year. The new vaccines had mixed results against the H1N1 flu virus when tested on mice, monkeys and ferrets (the closest model to human response to the flu virus): there was an immune response but not always strong enough to prevent infection. But it’s a promising step forward, nonetheless.

The iChip, used to discover the first new antibiotic in 30 years. Credit: Slava Epstein.

First New Antibiotic in 30 Years

Antibiotic resistance is on the rise among bacteria like MRSA. So the announcement that scientists had found the first new class of antibiotics in 30 years was a particularly welcome development. Teixobactin targets the lipid molecules that bacteria use to build new cell walls, and has proven effective against several pathogens, including highly drug-resistant strains of staph. It’s still in preclinical development, so don’t expect your doctor to be writing prescriptions any time soon. But it was the technology used to find teixobactin that generated the most excitement: a handy gadget called the iChip that lets microbiologists grow bacteria in dirt—a huge advantage because most soil microbes can’t be grown in the lab otherwise. The iChip has the potential to test thousands, perhaps millions, of bacteria looking for candidates with good antibiotic properties. Teixobactin could be just the beginning.

Krister Shalm adjusts the photon source in his Bell test experimental set-up. Credit: Burrus/NIST

Spooky Action at a Distance Is Real

Dubbed “spooky action at a distance” by Albert Einstein, entanglement is a quantum phenomenon whereby two subatomic particles can be so closely connected that one can seem to influence the other even across long distances. Three independent experiments this year have definitively shown that the phenomenon is real.

Physicists have been conducting variations of the so-called Bell test for decades with greater and greater precision, but could never quite claim to have produced definitive proof of spooky action, because there were still critical loopholes in the experimental design. Until quite recently, they simply didn’t have sufficiently advanced technology to close those loopholes.

Earlier this year, physicists at Delft University of Technology in the Netherlands sent two entangled electrons to separate corners of the campus and found that spooky action was real. Krister Shalm and his colleagues at the National Institute of Standards and Technology in Colorado closed those loopholes with greater precision than ever before, hammering the final nail in local realism’s coffin. A second team of physicists at the University Vienna conducted yet another version of the Bell test using one of NIST’s single photon detectors. They reported similar results, submitting their own paper to the journal Physical Review Letters at the same time as Shalm and his co-authors. Taken together with the Delft results, these loophole-free Bell tests should settle the question once and for all.

Mind-Melds With Rats and Monkeys

Star Trek fans are well familiar with Spock’s proficiency with the Vulcan mind-meld. But neuroscientists say something similar really does happen when brains are electrically linked to share impulses across a network. Two studies published this year in the journal Scientific Reports described work connecting rat and monkey brains, respectively, via electrodes, enabling them to coordinate their thoughts to carry out simple tasks, such as pattern recognition and moving a robotic limb. After all, it stands to reason that if more neurons from a single brain can do a job better, linking together two or more brains would be even more efficient than one.

Duke University researchers led by neuroscientist Miguel Nicolelis implanted two sets of electrodes in the brains of four rats and gave them a pattern recognition test to “solve.” Through trial and error, they found that the rats figured out to synchronize their brain signals. They acted in concert as a simple computer. The Duke team had similar results when they rigged up monkeys with brain-computer interfaces (BCIs). The three brain-linked monkeys were able to coordinate their efforts to manipulate a robotic arm. It’s still not Spock-worthy mind-melding, but it’s an exciting advance on the neuroscience front nonetheless.

Top image: New shape model of Comet 67P/Churyumov-Gerasimenko. Credit: ESA.