Q & A With Cassini Scientist Anthony Del Genio

Paging Tim Vazquez! ;)

I sent an email to Mr. Del Genio again, who was kind enough to answer my questions. Here's our latest email exchange:

--------------------------------------------------------

Hello Mr. Del Genio,

Yes, it's me again-the person who's fascinated with alien thunderstorms. :)

I was looking at this link:

http://www.spacetoday.org/SolSys/Saturn/Ca...SaturnNews.html

A quote:

"Cassini also discovered huge columns of thunderstorms on Saturn producing lightning bolts 10,000 times stronger than the most powerful on Earth."

Hmmm. I know how news sources tend to distort things. I used to read all sorts of conflicting info on the strength of Jupiter's lightning, until I finally emailed the folks involved with the Galileo spacecraft, and they told me that Jupiter's lightning is 1,000 times more powerful than Earth's.

This is the first time I've read about "colums of thunderstorms" on Saturn. Might they be really referring to the Dragon Storm?

Also-to get beyond Saturn for a moment, I've been reading up about Neptune, who's winds reach 1,250 mph, with its Great Dark Spot having winds of 1,500 mph-the highest wind recorded on any planet in our solar system (this fact being relayed by one of the Voyager spacecraft). Yet, I also read somewhere that Neptune's lightning is about as strong as Earth's.

Is that possible? Could there be lightning more powerful that's too deep to detect? Maybe it's just my ignorance talking, but for a planet to generate storms with 1,500 mph winds, I'd imagine thunderstorms there would be as powerful as those on Saturn, if not more so.

Take care.

Saul Trabal
----

Dear Saul,

Sorry to be so late in responding to your question, but I've been out of
town quite a bit.

Lightning has not been detected directly yet by our imaging cameras (we
have observations in the pipeline to try to do so later on in the mission),
but it has been detected indirectly by the Radio and Plasma Wave Science
experiment, which is run by Prof. Don Gurnett of the U. of Iowa. They
measure what are called Saturn electrostatic discharges, which are not all
that much different from the static you get on your radio when a
thunderstorm is in the area. They saw lots of that when the dragon storm
was present in our images, and so we all assume that it's due to
lightning. The dragon storm is indeed the "columns" of thunderstorms the
press release referred to, although we've seen other, smaller candidate
storms since then. I can't vouch for the lightning strength directly; I
saw an early JPL press release that said a million times stronger than
Earth's, but again, that's not my experiment's result.

As for Neptune, you have to distinguish between the mean large-scale winds
that are analogous to our jet stream, and the local winds associated with
thunderstorm outflow. The 1500 mph winds on Neptune are mean, jet-stream
type winds, and the reason they're so strong is that Neptune is a gas giant
planet and has much less friction to slow down winds than is true of
Earth's atmosphere, where the surface keeps things from moving too
fast. The speed of these large-scale jet-stream winds on Neptune has no
direct implication for the strength of thunderstorms and lightning. I'm
not sure what the evidence for lightning is on Neptune - we've only
observed that planet close-up briefly, and thunderstorms are very
infrequent on the giant planets, so I doubt we have a representative sample
of observations. If one is observing lightning optically (in images), then
it is indeed possible to miss stronger deeper lightning if it is so deep
that the flashes are attenuated before they make it up to the cloud tops
where we can see them, so stronger stuff at depth is a possibility on all
the major planets. On Jupiter, we probably can see almost anything since
the water condensation level is not so deep, but for Saturn, Uranus, and
Neptune it's possible that it's happening too deep for us to view from
space. For Saturn at least we'll have a chance to find out if we can see
anything over the next couple of years. The radio discharges, however, can
be detected from space even if they occur very deep.

Feel free to post anything I send you.

Regards,
Tony Del Genio
 
Back
Top