Impressive events of 2014 included the first landing on a comet. There were other stories that had great potential, but insufficient data to support their conclusions. Here are five stories that didn't meet Carl Sagan's precept: “Extraordinary claims require extraordinary evidence.”

1. Martian meteorite - evidence of life?
Carbon compounds on Mars were news in 2014. Also known as organic compounds, they're the basis of life on Earth. Curiosity rover found the compounds when drilling in Martian rock. Added to evidence of fresh water, this is good news for those searching for life on Mars. But a warning: not all such molecules are produced biologically.

The 2011 Tissint meteorite has fissures containing carbon compounds. It was twice intensively investigated, each time by an international team of experts. They agree that it came from Mars, and that the carbon molecules came with it. But how were they produced?

In 2014, investigators concluded that the molecules were biological in origin. “So far, there is no other theory that we find more compelling,” said Phillippe Gille in a press release from the École Polytechnique Fédérale de Lausanne in Switzerland. Yet the conclusion of another international team that analyzed the meteorite was that the carbon molecules were volcanic in origin.

There may be native biological molecules on Mars, but the evidence so far doesn't meet the Sagan Standard.

2. A large hidden planet?
Neptune, the most distant planet, is thirty times as far from the Sun as Earth is, i.e., 30 AU. The Kuiper Belt of small icy bodies extends from about 30-50 AU. There's indirect evidence of a spherical Oort Cloud – home of long term comets – surrounding the Solar System at more than 50,000 AU. What's between between the Kuiper Belt and the Oort Cloud is still debatable.

Sedna was discovered in 2003, its distance varying between 76-975 AU. It's clearly well beyond the Kuiper Belt, and the discoverers suggest that it's part of an inner Oort Cloud, a disc between the Kuiper Belt and the outer Oort Cloud. (Others disagree.)

Last year's announcement by Scott Sheppard and Chad Trujillo of the discovery of 2012 VP₁₁₃ got wide coverage. It was variously dubbed a dwarf planet, a probable dwarf planet or a possible dwarf planet. (I'd say the third is most accurate.) Its highly tilted orbit comes no closer than 80 AU to the Sun. It gets as far away as 452 AU. According to Sheppard and Trujillo, though not according to others, it's in the inner Oort Cloud.

It took ten years to find another object in the same part of the Solar System as Sedna, and this still makes only two data points. The discoverers claim that there may be thousands more of these bodies, and the press release from the Carnegie Institution of Science says that the discovery “indicates the potential presence of an enormous planet, perhaps up to 10 times the size of Earth, not yet seen, but possibly influencing the orbit of 2012 VP₁₁₃, as well as other inner Oort cloud objects.” Possibly, but where's the evidence?

Dark matter detected?
Dark matter is invisible, detected only by its gravitational effects on visible matter. There are ideas about what it might be, but it remains a mystery. Yet in 2014 three different groups of researchers published papers about detections of dark matter via X-ray emission.

3. Sterile neutrinos?
In studying the sky on galactic scales, two groups reported on the same emission line, one using NASA's Chandra X-ray Observatory, and the other ESA's XMM-Newton space telescope. They proposed that the emission could be from the destruction of sterile neutrinos, a hypothetical particle that is one dark matter candidate. They came to this conclusion because standard physics didn't seem to account for this emission.

It could be the start of an amazing discovery that would eclipse even the Higgs boson. Or it could turn out to be nothing much. The emission line in question is at the limit of the resolution of current X-ray telescopes, so further study must await a new Japanese X-ray observatory due to be launched in 2015.

4. Axions?
At Leicester University in England, a group analyzed fifteen years of data from XMM-Newton. They found an oddity, which was that the X-ray intensity was ten percent higher when observing the sun-facing boundary of Earth's magnetic field. Again, failing to come up with a conventional explanation for this anomaly, they suggested dark matter. In this case, they think it's particles called axions that produce the X-rays when they hit our magnetic field.

5. Cosmic inflation?
In March, researchers at Harvard University announced their discovery of gravitational waves using the BICEP2 telescope at the south pole. They'd found ripples in space-time from the birth of our Universe, evidence of cosmic inflation and support for the idea that ours is one of many universes.

Although feted as heroes in March, there were concerns. David Spergel of Princeton University said that what BICEP2 had detected was dust. He thought that the error came from a misinterpretation of data from the European Space Agency (ESA) Planck space telescope.

In June the Harvard team officially conceded that they might have underestimated the dust contamination, but didn't withdraw the paper. By September the Planck group said that dust alone could have produced the BICEP2 results. But they also said that it was still possible there was also a signal which would need further analysis to detect. We'll see.