Darker areas in the oceans, why? Earth Night Picture 1Oct'06

dcpattis · Post by **dcpattis** » Mon Oct 02, 2006 12:08 pm

Do the lighter parts indicate luminous life forms, and the darker a lack of same? Is it related to clouds on the day the picture for each section was taken?

craterchains · Post by **craterchains** » Fri Oct 06, 2006 2:16 pm

Correct this if it is wrong, but isnt that a picture looking up from earth to the heavens? Not down onto the earth and it's oceans?

Norval

dcpattis · Post by **dcpattis** » Sat Oct 07, 2006 2:37 am

The question refers to the 2006 Oct 1 Night Picture of Earth, http://antwrp.gsfc.nasa.gov/apod/ap061001.html. It seems that the images may contain unexpected information about the oceans encoded in the difference in brightness.

Nereid · Post by **Nereid** » Sat Oct 07, 2006 10:16 am

I moved this post to this section of NSL (Discuss an Astronomy Picture of the Day (APOD)), and changed the title (was: "Why are there darker areas in the oceans?")

craterchains · Post by **craterchains** » Sat Oct 07, 2006 1:36 pm

ohhhhhhh you mean this image'

http://antwrp.gsfc.nasa.gov/apod/ap061001.html

And I thought the reference was to a Night Sky Live image. Being posted in that part of the forum. Thanks for moving it to APOD Nereid.

Dcpattis may have a point about more information in the images. Many times discoveries are made years later by someone noticing things over looked by previous researchers.

Norval

rigelan · Post by **rigelan** » Sun Oct 08, 2006 7:19 pm

Could it have to do with the optical density of the oceans? The oceans had a certain brightness, but when it was stretched out to fit that particular earth-projection, that particular part got darker?

Or maybe some of the light of the oceans is actually reflections from the light of the moon, in which case the poles would get less just like they get less of the sun's light.

Or maybe the different coldness of the water affects the density of the water, which changes its albedo (ability to reflect light).

Maybe it has to do with wind/water currents or depths that change the relative shape of the wave in different locations, altering how it reflects light.

Can't say for sure, but these are my guesses. Maybe it'll spark someone to come up with a more complete answer.

BMAONE23 · Post by **BMAONE23** » Sun Oct 08, 2006 11:57 pm

It might even have something to do with the equitorial bulge of the oceans.

orin stepanek · Post by **orin stepanek** » Mon Oct 09, 2006 12:00 am

Could it be that the shallow areas have less color?
Orin

Dr. Skeptic · Post by **Dr. Skeptic** » Mon Oct 09, 2006 1:53 am

How about the composite photo is take in IR so warmer H2O shows brighter.

aichip · Post by **aichip** » Mon Oct 09, 2006 5:07 am

The actual reason might not be IR at all. Note that the spacecraft in use were meant to get good images using moonlight. Any person who has done astrophotography knows that with a little time exposure or wide aperture work, you can get excellent images using nothing more than moonlight.

I would suspect that what we are seeing is plankton or krill coloring the warmer waters and showing up faintly in that moonlight.

BMAONE23 · Post by **BMAONE23** » Mon Oct 09, 2006 5:48 am

Giving credit where credit is due, I e-mailed Mr R.Simmon to pose the question. If/when I hear from him, I'll post the reply as well as any provided explanation.

BMAONE23 · Post by **BMAONE23** » Wed Oct 11, 2006 2:31 am

Well,
Mr Simmon returned the answer:

Because it's fake! The background of the night lights image is a darkened and tinted version of a daylight composite image in which the color of the oceans corresponded to depth. I created a newer version where the ocean of the ocean is related to phytoplankton concentration, but the effect is small:

http://visibleearth.nasa.gov/view_rec.php?id=1438

He is right about the link being different

ckam · Post by **ckam** » Thu Oct 12, 2006 8:56 am

I couldn't find "newer version where the ocean of the ocean is related to phytoplankton concentration" with your link

BMAONE23 · Post by **BMAONE23** » Thu Oct 12, 2006 9:05 pm

I believe that the image links under "Images and animations" are the new image talked about. They do loose the reference to continents and seem to show only light concentrations. Mr Simmon did state that some things were lost and others didn't show well.

http://veimages.gsfc.nasa.gov/1438/earth_lights.gif