Dust Devils In Jezero Crater, single-point repository of imagery Options

[PDP8E]

SOL 301 -- 15 images -- 5 stances -- 1:40 PM
DD in stance 5
Here is just that sequence

[PDP8E]

SOL 302 -- 21 images -- 1 Stance -- Noon
Distant DD, center, wait for it...

[tau]

A "storyboard" an an animation of a dust devil on sol 308 during a Mastcam-Z multispectral photo series.
The Mastcam-Z filter number and the time in seconds after start of the series are annotated in the storyboard.
The difference-to-average method does not work here because of the spectral filters, therefore contrast enhancement was used.

[tau]

The dust devil on sol 308 continues into the infrared region of the spectrum with Mastcam-Z right eye filters 1 to 5.
The Mastcam-Z filter number and the time in seconds after start of the series in the previous post are annotated.
Contrast enhancement did not work here. Instead the difference-to-average method with manual adjustments to each image was used.
Overexposed and/or clipped highlights (link to the first raw image) in the bright landscape around the dust devil resulted in featureless patches of medium gray, which are masked here with red color.
A second dust devil appears in this series.
Starting with filter ZR5, the dust devils merge with the bright infrared background.

[tau]

Mastcam-Z images, an orthorectified HiRISE image, and a HiRISE digital terrain model were used to determine the route of the sol 308 dust devil on the ground.
Twenty control points of corresponding features were set in the Mastcam Z image and the HiRISE image.
With some measurements and calculations, pixel coordinates in the Mastcam-Z image could be transformed into map coordinates of the HiRISE image.
The length of the visible part of the dust devil's route is about 820 m.
The average horizontal ground speed was about 30 km/h, and even 36 km/h on average between second 0 and 57.
To verify the calculations, it would be interesting to see if the dust devil left a visible track.



Edit: corrected typo km/s to km/h (thanks to Floyd)

[Floyd]

Was the horizontal ground speed actually m/s not km/s?

[Deimos]

8.2 m/s, 30 km/hr.

[tau]

Was the horizontal ground speed actually m/s not km/s?

It was a typo. Of course, supersonic dust devils are not possible.

820 m / 100 s = 8.2 m/s = 29.52 km/h (rounded value 30 km/h)

I can't wait for the day when I don't make typos.

[rlorenz]

Mastcam-Z images......
The average horizontal ground speed was about 30 km/h, and even 36 km/h on average between second 0 and 57.

What is the diameter of the devil. Some years ago I identified an empirical law for the longevity of dust devils on Earth and Mars : Duration (s) = 40 * d^0.66 with d in m.

Apropos of this topic
Anyone interested in dust devils on Earth and Mars might enjoy my
Physics Today webinar to be held 2pm EST January 12, 2022 (I guess you
can view it online thereafter)
https://event.on24.com/wcc/r/3543264/A422D6...BBA18667191242C

[Bill Harris]

Mastcam-Z images, an orthorectified HiRISE image, and a HiRISE digital terrain model were used to determine the route of the sol 308 dust devil on the ground.

snip

I wondered about the possibility of transferring the DDs we see to a groundtrack on a map and seeing if a track was left.

--Bill

[tau]

What is the diameter of the devil. . . .

Here is a very rough estimate of the diameter of the dust devil using a scaled image.
The last three subimages where the dust devil begins to dissipate were not taken into account.
1 pixel corresponds to 0.76 m in nature.
Diameter of the brightes part where it touches the ground: 25 to 40 m
Diameter of the shadow: 60 to 70 m (local mean solar time was 11:09)
It was a nice coincidence that the dust devil entered the field of view exactly at the moment when the image series started.

[tau]

I wondered about the possibility of transferring the DDs we see to a groundtrack on a map and seeing if a track was left.
--Bill

Groundtracks on a map can be reconstructed only if we see in the photos the point where the dust devil touches the ground. In most cases this point is hidden behind local elevations.
For example, in this image a second dust devil emerges to the left from the existing one. However, its distance from the rover can be anywhere between 50 m behind the nearest ridge and 7000 m on the inner slope of the crater wall.

[tau]

Control points are necessary to tie a photo taken by the rover to an orthorectified orbital photo.
Here are my 20 control points. Some small features are hidden by the crosses.
In this case, it was of great advantage that the dust devil passed a smooth slope with an incline towards the rover.

[PDP8E]

Sol 372 DD watch
21 images - 11:40 AM



(I have a backlog of DDs -- broke my wrist -- sold my house - moved to a new one -- crashed PC -- but all set now....)

[Bill Harris]

Be well!!
Looking forward to the Backlog.

--Bill