The Blue Marble "super-contrail"

Trailspotter

Senior Member.
Created in 2002, this spectacular “blue marble” image was the most detailed true-color image of the entire Earth to date. Using a collection of satellite-based observations, scientists and visualizers stitched together months of observations of the land surface, oceans, sea ice, and clouds into a seamless, true-color mosaic of every square kilometer (.386 square mile) of our planet.

http://visibleearth.nasa.gov/view.php?id=57723

The Blue Marble is the original iPhone's default screen, which have been seen by millions of iPhone owners and by everyone who has read about the iPhone since 2007. I still have it on my iPhone, whereas a larger version of this image regularly pops up on my laptop screensaver.

But what puzzles me in this particular image of Western hemisphere is the origins of a straight white line that goes diagonally from the Southern tip of Greenland across the Labrador Peninsula to the Southern shores of Hudson Bay. This line coincides with a major air traffic route between Europe and the USA West Coast, but, given the scale, it appears to be too wide for a contrail. So, what is it: a composite of many parallel contrails that happened to occur in that area on the day of filming, or an artefact of stitching of many small images? Or is it something else?
 
Last edited:

WeedWhacker

Senior Member
But what puzzles me in this particular image of Western hemisphere is the origins of a straight white line that goes diagonally from the Southern tip of Greenland across the Labrador Peninsula to the Southern shores of Hudson Bay.
I would guess it is just an image artifact.

Others? Please chime in.
 

Mick West

Administrator
Staff member
(image contrast enhanced)


There seems to be other thin cirrus clouds next to it. Possibly just a weather front that's unusually straight?
 

Ross Marsden

Senior Member.
Jetstreams (clear to poleward, cloudy to equatorward) can produce long straight line cloud features.
This one looks very long and straight, and not really jet-cloud looking.
Looks like genuine cloud and not contrail, though.
There don't appear to be any other obvious image artifacts. I would hope not with all those scientists and visualizers working on it.
 

Trailspotter

Senior Member.
There seems to be other thin cirrus clouds next to it. Possibly just a weather front that's unusually straight?
I do not know. As far as I understand, this image was a compilation of the MODIS images taken by the Terra satellite in its first year of operation. There are orbit swath images that go back to the beginning of 2001, but I have not figured out when the images selected for this area were taken:
http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/realtime.cgi

Still, there probably were enough images to avoid a stitching artefact of this kind. In contrast, there is nothing like it in the Eastern Hemisphere image made at the same time:
 

Mick West

Administrator
Staff member
I do not know. As far as I understand, this image was a compilation of the MODIS images taken by the Terra satellite in its first year of operation. There are orbit swath images that go back to 2001, but I have not figured out when the images selected for this area were taken:
http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/realtime.cgi

Still, there probably were enough images to avoid a stitching artefact of this kind. In contrast, there is nothing like it in the Eastern Hemisphere image made at the same time:
Except for this. Much thicker, but still long and straight
 

Trailspotter

Senior Member.

Mick West

Administrator
Staff member
I remember this thread, but I do not think that it presents a comparable case. Here we see an artefact of automated processing of daily satellite images, whereas the Blue Marble image was custom-made. It was one of the early exercises in a high-resolution imaging of the whole planet surface.
I agree, it was just for comparison.

I think is an actual natural cloud structure, but perhaps more isolated than normal due to the composite nature of the image.
 

Pete Tar

Senior Member.
A contrail wouldn't be that big, that's a huge cloud front.
It seems to go over the circular system and retain a separate layer from it, but I guess that represents two different weather systems at different times put together?
How far away is the (hypothetical) viewer in this shot?
 

Trailspotter

Senior Member.
I think is an actual natural cloud structure, but perhaps more isolated than normal due to the composite nature of the image.
A contrail wouldn't be that big, that's a huge cloud front.
It seems to go over the circular system and retain a separate layer from it, but I guess that represents two different weather systems at different times put together?
How far away is the (hypothetical) viewer in this shot?
It may well be a natural cloud structure. I've seen long linear cloud formations on satellite images before, in particular, this remarkable image taken over Eastern Australia on March 3, 2011:

Its inland part is about 550 miles long but only 30±10 miles wide, it goes in a straight line from East to West across NSW and above Sydney, after that it continues over Pacific for 250 miles more, widening before merging with other clouds.

When viewed on Google Earth from about the same distance of 7000 miles, its dimensions are comparable to the linear structure in the Blue Marble image, albeit it looks a bit wider:
Australian line cloud.jpg

Seeing the original "raw" images for the latter may give a definite answer, but I do not know whether these images are available or not. Posting the thread, I thought that an answer might have been found already, given the age and popularity of the Blue Marble image. However, it appears that no-one has asked the question about the origin of its linear cloud formation before. :cool:
 

Mick West

Administrator
Staff member
Nearly raw files are available here:
ftp://neoftp.sci.gsfc.nasa.gov/bluemarble/



The general cloud structures are on cloud.W, but with no line


And can be seen combined with some others in cloud_combined, still with no line:


But the line shows up in land_ocean_ice_cloud



So it's a blending of more than two images. It's not clear even where the underlaying clouds of .combined come from, and I suspect there was some artistic blending going on of multiple images.
 

Trailspotter

Senior Member.
So it's a blending of more than two images. It's not clear even where the underlaying clouds of .combined come from, and I suspect there was some artistic blending going on of multiple images.
I knew I should have used a different title for this thread to grab more attention ;). How about:
Apple spreading out NASA subliminal contrail images :rolleyes:

But I still think this line represents an observed cloud formation in this area, whatever natural or man-made. I will continue looking for confirmation, but it probably will take a while to find one.
 

Trailspotter

Senior Member.
I think I have found a probable origin of the linear cloud structure in the NASA Blue Marble (2002) image.

The info at http://vterrain.org/Imagery/WholeEarth/ describes it as:
"a 1km global image composited from the MODIS and AVHRR satellites, collected June through September 2001".

I went through the MODIS images for that period at http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/realtime.cgi, but found no similar formation in this area. However, I found one further south, off the North America East Coast in the images taken on August 1, 2001:


I rescaled this image and aligned it to the coastline in the Blue Marble image:
blue marble contrail.jpg

The Blue Marble line is similar to this formation in shape, dimensions and orientation and therefore probably has been derived from it and translated further north for an unknown reason
 
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