A glimpse of big-hearted Pluto and other big science moments of 2015

When you cast an eye back over 2015 for the standout science stories, majestic images of our galactic neighbours cannot fail to capture your gaze.

In July, Nasa's New Horizon probe sailed close to Pluto and its moon Charon, out at the fringe of our solar system. The visual feast that poured back from that fly-by was stunning. Nasa released images to the public that showed mountains, layered craters, pitted and icy plains on the surface of Pluto and canyons and landslides on Charon.

Particularly captivating was a heart-shaped feature, estimated to be 1,000 miles (1,600km) across at its widest point, on Pluto's surface. It prompted a "wow" from New Horizons principal investigator Alan Stern: "My prediction was that we would find something wonderful, and we did. This is proof that good things really do come in small packages."

We got closer peeks at other celestial neighbours, too. This year Nasa's Cassini spacecraft performed close fly-bys of Saturn's icy, geologically active moon, Enceladus – including one that passed only about 30 miles (49km) above the moon's south polar region.

Mars, too, offered its own revelation: evidence that salty water flows intermittently on the red planet. Using an instrument aboard the Mars Reconnaissance Orbiter, researchers analysed spectral details of streaks called "recurrent slope lineae" on the Martian surface that change depending on the season. "Our findings strongly support the hypothesis that recurring slope lineae form as a result of contemporary water activity on Mars," they wrote in Nature Geoscience.

Gene editing

Closer to home, gene-editing technologies have been making strides and turning up the dial both on controversy and opportunity.

Scientists in China reported they had applied a gene-editing research tool called Crispr/Cas9 to human embryos. Their paper reported a “pressing need to further improve the fidelity and specificity of the Crispr/Cas9 platform, a prerequisite for any clinical applications of Crispr/ Cas9-mediated editing”, as well as fuelling ethical debates around the approach.

A different form of gene editing grabbed the headlines when doctors at Great Ormond Street Hospital in London used it “ex-vivo” to treat a one-year-old girl who had relapsed acute lymphoblastic leukaemia.

The toddler received donor immune cells that had been exposed to DNA- cutting enzymes to tailor their response to the disease and to the anti-cancer drugs, and she later received a bone-marrow transplant to rebuild her blood and immune system.

“We have only used this treatment on one very strong little girl, and we have to be cautious about claiming that this will be a suitable treatment option for all children,” said Prof Waseem Qasim. “But this is a landmark in the use of new gene- engineering technology, and the effects for this child have been staggering.”

Nobel for Campbell

This year also saw the second Nobel laureate in the sciences from Ireland. On December 10th, William Campbell received the award in Stockholm, sharing it for work on the anti-parasitic drug ivermectin, a treatment for river blindness in humans.