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Close Mars Means Close-Up Pictures
Guttata writes " space.com has posted 1 of 2 images taken by Hubble last night, dubbed the best Mars globe photo ever taken. The second image will be posted at 4 p.m. ET. Cool!"
aderuwe points to a report on the Hubble site itself. Finally, dpp writes "Space.com is reporting how astronomers using the UK Infrared Telescope (UKIRT) here at the Joint Astronomy Centre have made what are thought to be the sharpest ground-based images of Mars to date. They'll be studying the spectra of the infrared light to look for the signatures of minerals that would indicate the past presence of liquid water, which could have hosted life."
If you want a great Mars pic from last night for your wallpaper (suitable for 1024x or 1280x) today, get it here:
/ full_jpg.jpg
wget http://hubblesite.org/db/2003/22/images/a/formats
It's pretty slow loading, but wget will get it for ya.
CB
free ipod and free gmail!
"Recent studies have hinted at liquid water on the dusty planet."
presumably those studies aren't quite as recent as the one last week which found that Mars isn't watery now, and wasn't in the past:
http://news.bbc.co.uk/1/hi/sci/tech/3173167.stm
There are some very good examples online if you search. The image stacking seems to reduce the effect of atmospheric turbulence. The effects of the air are always changing and so they tend to average out whereas your target (Mars in this case) will remain constant.
Here is a site that explains image stacking.
I think they even do this with Hubble imagery.
Another finishing trick is to snap some dark frames and subtract that out of the final image to remove effects of the image sensor itself.
--- Ban humanity.
Marco--
I know a bit about this. Basically, the idea is to correlate and overlap information from several individual exposures, while "dewarping" the variations caused by the target rotating during the scan. David Hilvert has written an open source tool that implements some basic methods for doing this kind of work; it's called ALE. Google for "Superresolution" for further information; everything that goes from the temporal domain to the spatial domain ends up using techniques like this.
--Dan
And they have sent probes to Venus. There's even some ground based images from a Russain lander, but they don't show very much. The surface has been fairly well mapped by radar bearing probes from the US.
href="http://zebu.uoregon.edu/~js/ast121/lectures/ surface_venus.html">The surface of venus.
--- Ban humanity.
Yesterday's APOD was exactly this kind of image using the same kind of technique.
see http://antwrp.gsfc.nasa.gov/apod/ The resolution is a bit better. For an even better image, see http://antwrp.gsfc.nasa.gov/apod/ap030824.html
Maybe they're referring to the Cassini mission that arrives at Saturn next year? Here's a good site for basic info.
In illa quae ultra sunt
What you need is something more like the VLA in the optical, where you have multiple axis you resolve and multiple baseline widths to incresase your spatial sensitivity. But even then there is the spatial frequency problem. As interferometry is good at resolving objects right around its resolution limim, Larger structure is lost in the forier transform. So to improve that you need more elements packed closer together. This, in the limit of maximizing the image quality, is a single mirror.
So in reality, if you want a good image its best to launch a BIG single mirror telescope than a bunch of smaller ones and do interferometry. Its just much cheeper to do the later.
Today is a gift. Save the receipt.
Mars and earth currently are in opposition (which is why they are so close), meaning than mars, earth and sun lie on one straight line. If you were looking at earth from mars, your eyes would hurt, because you'd be staring right at the sun behind the earth.
Alex
Heisenberg may have been here
While I wouldn't 100% put it past NASA to do a little color-correcting (REAL easy to do with RGB imagery) it's entirely plausible that the Martian sky could vary all the way from an Earth-style high-altitude deep blue to a total-sunset deep red. The big governing factor will be the dust content of the air.
The dust content, of course, will be highly variable from total during a dust storm, to fairly little. I'm not sure (and perhaps no one is) whether there are ever 'dust free' days on Mars, or if there is always some small amount of dust sufficient to keep some reddish hue 24/7/365. Or rather 24.8/7/580 or whatever (I forget the number of Martian days in a Martian year).
But to expand a bit on Mr Birdman's explanation, all normal gasses (O2, N2, CO2, probably even H2S and H2O in gas form, but not in aerosol form) will look blue, due to the aforementioned 'Rayleigh scattering'. Basically light (and all other forms of EM radiation) is scattered if it hits any object that is near or larger than its wavelength. Blue light, with its shorter wavelength, is scattered more by air molecules, so you see more blue light from the sky than red. This will happen in the upper atmosphere.
If there's also dust, which will scatter red light as well as blue, you will see more red than blue. This is because the there is a higher intensity of red light in sunlight than blue, coupled with the fact that shorter wavelengths are getting scattered away and losing intensity before they reach the lower atmosphere where the dust resides. Aerosols in the atmosphere will act much like dust.
Disclaimer: I'm pretty much going on memory here, and didn't google this to check my facts. I am especially unsure of my explanation of why dust and aerosols look red. There may be more to it than that.
if ($it != $onething) {$it = $another;}
Are we talking about bacteria that might survive the interstellar trip and all its radiation [...] he former seems like a very low risk
;)
First, it's an interplanetary trip -- there's a big difference.
Second, we already have an example of bacteria surviving on a space probe. Some Streptococcus mitis survived Surveyor 3's trip from the Earth to the Moon and the two and a half years of exposure to vacuum, temperature extremes, and radiation between when it landed in April, 1967 and when the Apollo 12 astronauts took some parts of Surveyor 3 back home in November, 1969.
Given our very small sample size of spacecraft returned for analysis and the fact that one showed surviving bacteria, I don't think one can qualify the risk of bacterial survival as "very low." When dealing with a situation in which a single bacterial spore could compromise the ecosystem of an entire moon, it pays to be cautious.
Never underestimate the bacterium -- it's been through more shit than you can imagine