Let me give you another Earth. Yup, a whole new planet. Of course, there are conditions. We don't really know what the atmosphere is like. We're not totally sure about temperatures. Don't ask about the geology or oceans. As for it being inhabited or inhabitable, we can't really say.

That's the scenario that played out in July this year when NASA announced the discovery of Kepler 452b, a planet that has some measurable properties consistent with our own. Media reports around the world advertised it as Earth 2.0. Soon after the story broke, this analyst was taking questions from reporters on a prominent news channel. What was life like on this planet? The anchorwoman was stunned when it was explained that we didn't even know if the planet could support life, let alone know of any life that was there.

This scenario has played itself out too often, with other recently discovered exoplanets. It has also happened too much with Mars exploration. NASA does marvelous things with science, but it completely oversells the results.

It's a tough world out there. You need to show a return on your investment. Those who return the greatest bounty receive the best treatment. Those who don't sometimes lose everything. Science is caught up in this vicious cycle, and such events can be found well beyond NASA. They sometimes produce outright scientific fraud. This is not to suggest that any of NASA's scientific work is illegitimate, but NASA's beatups of real scientific results are discrediting the fine work that the agency and its associates regularly accomplish.

NASA is lucky that this hasn't backfired more. The media either doesn't receive or issue reality checks on the big claims. The news cycle moves on. Yesterday's big story is forgotten. But after so many discoveries that don't live up to the hype NASA generates, some resistance must be accumulating.

NASA needs to stop advertising so many exoplanets as Earthlike. This has connotations with the general public that are vastly different from the way planetary scientists think. Venus is in some ways Earthlike, being small and rocky, yet few people would call it anything close to a second Earth.

Similarly, we all know by now that there is water ice on Mars and plenty of evidence to support the idea of liquid water in the past. There could even be liquid water today in some underground areas. So NASA really needs to stop speaking of these matters as breakthroughs every time we find more evidence of this. We also need to tone down the "life on Mars" hints, which have been festering since the ALH84001 meteorite controversy of 1996.

We would also like to see human footprints on Mars, but NASA presently has no spacecraft for getting its own crews to Earth orbit. There's no chance of sending astronauts from NASA or any other space agency to Mars in the next few years. NASA's regular references to a human spaceflight program to Mars (including the hype surrounding the first Orion capsule test) are probably sowing false hopes in many people. Yes, we will eventually get to Mars, but there is simply too much talk about a program that does not exist, and will not exist for quite some time.

The media won't blindly swallow PR lines so readily in the future. Eventually, even scientifically illiterate editors will start to notice that something's strange with NASA's spin doctoring. Cynicism has permeated the scientific media for a long time. That cynicism will spread. Similarly, much of the public would know that NASA is overhyping its work. This makes it difficult to build trust and support for an agency that finds itself increasingly short of friends.

Like any group doing good work, NASA has a right and an obligation to report on its achievements. This is especially true for a government agency. There are plenty of good things happening at NASA. Let the true facts and the real discoveries speak for themselves. Otherwise, nobody will believe NASA's most amazing feats when they truly deserve to by hyped.

Dr Morris Jones is an Australian space analyst who has written for spacedaily.com since 1999. Email morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email. Dr Jones will answer media inquiries.