Top 25 stories of 2013, from microbes to meteorites

Last year it was easy to choose a story to lead our annual Top 25 list. The discovery of the Higgs boson was a watershed moment, ending a decades-long quest by thousands of physicists to fully describe the subatomic realm.

This year, nothing so momentous came to pass. But science isn’t just about dramatic announcements and tremendous technical feats. Anyone who reads Science News regularly appreciates that great new insights often arise from countless little bits and pieces of new knowledge. This year, careful readers may have noticed a steady accumulation of revelations about the bacterial communities that call the human body home. It has long been known that those microbes are essential to processes like extracting nutrients from food and fighting off their less benign brethren. But this year a growing body of research demonstrated that bacteria engage their hosts so vigorously that in some situations, scientists are left wondering which party is the tail and which is the dog.

Human evolution has also produced an impressive body of new knowledge, though some of it only deepens existing mysteries. For example, the oldest hominid DNA ever analyzed linked 400,000-year-old bones from Spain not to the Neandertals that later dominated the region, but to mysterious early hominids known from sites thousands of kilometers to the east. It will probably be a few more years before anyone can explain what is becoming an increasingly controversial era of human evolution.

This year also demonstrated that big findings can be big letdowns. After a spectacular landing on Mars in August 2012, the Curiosity rover looked for elevated atmospheric methane concentrations that would have been telltale evidence for the presence of microbial life. Anything over a few parts per billion would have given us a clear choice for 2013’s top story. But Curiosity detected an average methane concentration of only 0.18 ppb, a finding that landed it in 17th place.

Science News Top Stories of 2013

1. Your body is mostly microbes
   Microbiome results argue for new view of animals as superorganisms

2. Bioengineers make headway on human body parts
   New techniques produce mimics of brain, liver, heart, kidney, retina

3. Planck refines cosmic history
   Satellite hints at slower expansion rate for universe

4. New discoveries reshape debate over human ancestry
   Relationships among early hominids disputed

5. A double dose of virus scares
   MERS, H7N9 join list of potential pandemics

6. Sleep clears the cluttered brain
   Gunk between cells is cleansed during slumber

7. High court rules against gene patents
   Justices open way for choices in DNA testing

8. Language learning starts before birth
   Babies seem familiar with vowels, words heard while in womb

9. Caffeine triggers cloning advance
   Human embryonic stem cells copied successfully

10. Carbon dioxide levels pass milestone
    Panel affirms humans’ role in warming

11. Putting kids at risk
    Parents lax on vaccinations
     
12. Voyager 1 reaches interstellar space
    Planetary probe is first to pass beyond heliosphere

13. Death of a planet hunter
    Kepler ends successful mission

14. Below absolute zero, but hot
    Lab trickery achieves negative temperature

15. DSM-5’s controversial debut
    Diagnostic manual updates disorder criteria

16. Obama unveils brain initiative
    Project to seek secrets of thinking, learning

17. Methane shortage on Mars
    Trace of gas not enough to be sign of life

18. Canine genealogy
    Competing clues confuse story of dog domestication

19. Dark energy gets more confusing
    New data raise prospect of ‘Big Rip’ destroying cosmos

20. Slain king’s bones dug up
    Richard III’s skeleton reveals fatal wounds

21. Progress made toward twin prime proof
    Surprising advance sparks flurry of work on mathematical conjecture

22. Visitor from the Oort cloud
    Comet ISON meets demise in solar flyby

23. Odd cicada history emerges
    Brood II returns better understood

24. Gift of steroids keeps on giving
    Mouse muscles stay juiced long after doping ends

25. Meteorite makes an impact
    Space rock fires a warning shot