Scientific data sharing has become big news in the wake of the theft of e-mails from the Climatic Research Unit and ensuing investigations. Although the CRU researchers appear to have had an attitude towards data sharing that breached generally accepted scientific ethics, the process of actually sharing the data would have been anything but straightforward. The CRU had no procedures in place for data sharing, the data came from a variety of sources with no standardized data format, it was a mix of published and proprietary information, etc. In short, it's one thing to decide to share the data, another challenge entirely to actually do so.

You can contrast this with NASA, which has procedures in place for sharing data and a standard policy for publishing it. But, according to a report produced by Nature News, the agency may only be sharing a deliberately limited version of the data from its planet hunting probe, Kepler.

Sharing data is considered an essential part of science because it allows others to verify and build on a research group's work. In most circumstances, however, researchers are allowed to keep data confidential until publication. This enables them to receive credit for their work, and allows them to perform a rigorous analysis before turning work over to the wider field for consideration. NASA typically allows the primary mission scientists a fixed period of time to perform data analysis and prepare publications before data from its hardware is released publicly.

This creates a bit of a problem for Kepler data, because the team involved has set rigorous standards for discovery: any signal that suggests a transit of a planet in front of a host star would have to be observed several times before being considered an indication of the presence of an exoplanet. For planets orbiting close to their host star, this could be done in a matter of weeks. But for objects with a more Earth-like orbit, several years will be required.

Releasing the entire data set as it arrives, or even after a year's delay, could allow anyone who's not interested in the sort of high standard set by the Kepler team to publish evidence of even single transits. Until follow-up observations either confirmed the result or indicated it was a false positive, it would be in the literature. That's not a huge problem for scientists—most researchers in the relevant fields would probably be quite aware of the limitations—but it could definitely influence public perception and space policy decisions.

The alternative extreme would be to keep the whole data set under wraps until a full analysis was completed. There's no indication that NASA is considering this, for good reason. The Kepler team has been very specific about the sorts of data that make it through its analysis pipeline; most of the 100,000 stars in its observation field won't make the cut. But that doesn't mean that a given star will be completely uninteresting; it's possible that the data will provide valuable information for other areas of research. So, not releasing any data may actually hold back other scientists.

The compromise that's now being considered is to release data on everything but 400 "objects of interest" that the Kepler team has flagged for follow-up (the release would come on schedule in June). The Kepler team would be able to continue evaluating these objects until February of next year. Even that isn't sitting entirely well with the astronomy community; the Nature reporter talked to several astronomers who felt that the more eyes on the data, the better the chances that promising-looking results could be rigorously evaluated.

Regardless of what the ultimate decision is, the data will eventually be released. But the actual timing and content of the releases in the near future will depend on a careful consideration of a number of competing issues. And this is a relatively simple situation; in contrast with things like genome data, the stars don't have to provide informed consent. And about the only ones likely to think that astronomers are engaged in a conspiracy are a few UFO nuts.

On the positive side, the Kepler team seems to be very good about quickly announcing and publishing their work.