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The first direct evidence of lightning has been detected on Mars. Researchers from the University of Michigan found signs of electrical discharges during dust storms on the red planet using an innovative microwave detector . The bolts were dry lightning, said Professor Chris Ruf. “What we saw on Mars was a series of huge and sudden electrical discharges caused by a large dust storm. Clearly, there was no rain associated with the electrical discharges on Mars. However, the implied possibilities are exciting.”
The Space Physics Research Laboratory at the University of Michigan developed the kurtosis detector, which is capable of differentiating between thermal and non-thermal radiation. The device took measurements of microwave emissions from Mars for approximately five hours a day for 12 days between May 22 and June 16, 2006.
On June 8, 2006 both an unusual pattern of non-thermal radiation and an intense Martian dust storm occurred, the only time that non-thermal radiation was detected. Non-thermal radiation would suggest the presence of lightning.
Electric activity in Martian dust storms has important implications for Mars science, the researchers said.
“It affects atmospheric chemistry, habitability and preparations for human exploration. It might even have implications for the origin of life, as suggested by experiments in the 1950s,” said Professor Nilton Renno of the university’s Department of Atmospheric, Oceanic and Space Sciences.
“Mars continues to amaze us,” said Michael Sanders, manager of exploration systems and technology at the National Aeronautics and Space Administration’s Jet Propulsion Laboratory and a researcher involved in the study. “Every new look at the planet gives us new insights.”
The new findings are to appear in an upcoming issue of the journal Geophysical Research Letters.
Source: University of Michigan
Just where is that ‘kurtosis detector’, and by the way what is ‘kurtosis’ exactly?
Funny that the linked paper doesn’t give a clue.
I googled it, read the technical articles, and I *still* don’t have a clue what a kurtosis detector. Here’s the Wikipedia article on what a “kurtosis” is:
Triboelectric whirlwinds sounds about right.
In fact the recently observed magnetic tornado’s at Mercury grooves right in there with the idea that the ‘Dust Devils’ seen on Mars may even be triggered by similar currents.
@ Aqua:
Yes, that is a distinct possibility, Martian dust devils have been detected that aren’t part of a general dust storm. The atmosphere is very thin, so general principles of convecting “air” masses has less probative value. Vortex structures are known to transport electricity. Martian dust devils are not your average dust devils, they are much taller than generally on Earth.
They could be as a result of impinging electrical currents from above, although Mars doesn’t have a well organized magnetosphere, but a rather spotty one.
@ Manu and Dave Finton:
roughly: kurtosis is a measure for how much individual measurements deviate from the expected distribution – which is the familiar “bell curve”. I guess the detection of unexpected kurtosis provided the tip-off that those discharges were happening.
@ Anaconda: Phoenix shot some movies of those Martian dust devils, and one of them hit it square-on. They are actually rather “wimpish” compared to dust devils on Earth, according to Phoenix on Twitter. The artist’s mock-up illustrating this article doesn’t show anything like what they really look like. They are wispy, ghost like… but quite tall due to the lower gravity. There isn’t much magnetism to speak of on Mars.
Now, those huge global sandstorms… that’s a different story!
Thanks Dave & Feenixx!
This sounds a bit, ah, pseudo-scientific, doesn’t it?
So there are ‘detectors’ for abstract math concepts?!
(In fact, as suggested in the Wikipedia link, a coin toss is one!)
Maybe we should understand that the team developed a microwave detector, and used its data to calculate kurtosis?
Which gets me back to my first question: where is that detector? Is Earth a possibility considering atmospheric absorption?
Oh, snap! Basically, “kurtosis” is to statistics what “snap” is to physics. [Statistics moments: mean, variance, skewness and kurtosis. Analogously physics time derivatives: relative velocity, acceleration, jerk and jounce (snap).]
I should know about these detectors, but didn’t. No problem, by the power of Google invested in me I find that: recently it has become popular to base microwave detectors for interference on kurtosis, because thermal sources have a fixed (gaussian) kurtosis. The power level of the source conveniently drops out of the detection, which becomes unbiased.
This paper finds that low-noise microwave devices have such a kurtosis.
Conversely, a different kurtosis is a good measure of non-thermal, high-noise microwave sources so are used for RFI, radio frequency interference, detection in microwave radiometers. The first link I gave is Ruf et al paper on how they constructed and verified their setup. They found that sources with 50 % duty cycle could of course not be detected with kurtosis, but that for example radars with 0.1 % duty cycle was detectable at (roughly) SNR ~ 0.01.
Such a detector can be constructed by “a square-law detector and a high-speed analogue multiplier”.
I guess Earth absorption would be roughly thermal as this was the basic level (after the detected MRO signal kurtosis skew had been accounted for). So remaining signals in the absence of Earth lightning and radar RFI would be Mars lightning.
Google “Space Physics Research University of Michigan kurtosis detector”
http://ursi-test.intec.ugent.be/files/URSIGA08/papers/JFp8.pdf and lots more.
This was performed in 2006. Were the results not available until now?
Bill
Oh, and the GRL paper _did_ contain a reference to the detector paper, which in turn describes the setup in general. (They should be happy to provide details inf anyone care to repeat or expand on the work.) In fact, they referred to it already in the introduction.
Why the results were slow? Perhaps because they wanted to find more events, but seems to have lucked out. Maybe this also made the journals reluctant to publish – seeing the publication name, this should formally be an announcing “letter” informing basically on progress, not a paper on results.
Thanks Wjwbudro and Torbjorn!
This is starting to make sense (for me).
There is no such thing as a Kurtosis Detector, but there is a Kurtosis-based Radio Frequency Interference Detector.
Now, since it sorts thermal emissions from non-thermal, it might see trough Earth’s atmosphere all right, although my first thought would have been that Earth’s atmosphere (also) blocks radiation.
This ability could have some nice applications in astronomy…
interesting
Tay… Are Tribo-electic fields scaleable? Magnetic tornado’s at Mercury, Earthly tornado’s then Martian Dust Devils, being evidence of mag. field interactionszuh?
How tall are these dust devils?
Mt. Everest sized?
If so, then that seems way to tall and powerful for simple thermal friction of dust particles to generate such a tall vortex.
Could it be their confirmed electrical is not simply “rubbing dust together”, but is due to larger electrical systems on Mars?