No scientist ever claimed to know what dark matter is. How could you falsify the idea of "we don't know yet"?
What you most probably mean, is that some scientists might have brought forward ideas to explain what dark matter is and that THOSE ideas were falsified. But "dark matter" itself is not an idea. It's a name for something that measurably exists but of which we don't know what it is.
*If* you were correct that NASA and the mainstream were making no claims about dark matter, I would not be publicly busting their chops over their claims. You are however naive in terms of what they actually claim about the nature of "dark matter" IMO, particularly their need for "exotic" types of matter to make their nucleosynthesis numbers work right.
NASA does unfortunately run around making "knowledge statements" about the composition and makeup of "dark matter" that simply cannot be supported by the evidence:
Dark Energy, Dark Matter - NASA Science
By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?
We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter.
Emphasis mine. Each of those three highlighted claims were actually *falsified* since that lensing study in 2006, and they have been *falsified* repeatedly.
In 2009 we finally figured out that we *botched* the star count something terrible, falsifying their claim about it *not* being in the form of stars.
http://www.jpl.nasa.gov/news/news.php?feature=2287
We also found they blew the second claim too.
2008 | Universe shines twice as bright | University of St Andrews
It turns out it *was* absorbing more light passing through them than we realized.
The third claim is simply and utterly absurd.
New Telescope Strategy Could Resolve Dark Matter Mystery, Scientists Say | Space.com
We see gamma rays coming from *all over the place* in space, from solar flare activity, to electrical discharges in planetary atmospheres. Instead of attributing these events to discharges and antimatter, they simply chalk them up to their supposedly *dark* friends, and now claim they "produce light"!
Every single one of those highlighted claims has been falsified since 2008, but NASA and the mainstream continue to make them anyway.
They didn't even update any of those numbers on that website based on any of the revelations of stellar miscounts or brightness factors, or even all the plasma they found in 2012. In fact the *only* time they've updated that particular page was to change the percentages *only slightly* due to the nucleosynthesis calculations related to PLANCK data.
They *need* exotic forms of matter, otherwise all their nucleosynthesis claims go up in smoke.
NASA has continuously and erroneously misrepresented the facts about the *makeup* and compositions of that "missing mass". As you said, they do *not* actually know what dark matter is, or is not. They do however erroneously misrepresent the facts in terms of what we actually can say about it.
The whole draw of SUSY and WIMP theory is due to the fact that it doesn't "mess up" their claims about nucleosynthesis, whereas *ordinary* matter would mess it up big time. The "creation mythos dogma" must be protected and promoted at all costs, even at the cost of scientific honesty and integrity.
They don't even *care* that SUSY theory took three straight hits in the lab in the past 18 months, they *still* keep writing about SUSY theory on nearly a *daily* basis, including trying to claim that WIMPS are the cause of gamma rays in space!