What would aliens be able to tell about earth from their home stars?

assume thier tech is at our level or just slightly more advanced.

phys.org...

"We're trying to think about how to use observations of the Earth itself to understand the kinds of things we'll be able to do in the future with possibly the next generation of telescopes," said Robert Fosbury, an emeritus astronomer with the European Southern Observatory (ESO) who participated in the research.

[snip]

The paper, "High resolution transmission spectrum of the Earth's atmosphere: Seeing Earth as an exoplanet using a lunar eclipse," is available on the pre-publishing site Arxiv and has been accepted in the International Journal of Astrobiology.

[snip]

After removing some effects generated by the local atmosphere, the researchers examined the spectrum of colors to see what molecules were visible. A few surprises popped up.

For example, they didn't see as much water vapor in the signature as observers saw in a 2009 eclipse that encompassed much of the Northern Hemisphere. (That paper, "Earth's transmission spectrum from lunar eclipse observations," was published in Nature.)


[snip]

Another surprise was the abundance of nitrogen dioxide. Normally the nitrogen dioxide is regarded as a pollutant produced by human activities. The Antarctic, however, is quite a barren location—but it did have a volcano.

[snip]

Ozone on other planets

If we were to look at Earth as an exoplanet, could the nitrogen dioxide be interpreted as a sign of pollution, of microbial life or of a volcano? Fosbury said it depends on context. If the planet had an abundance of volcanoes on its surface, you would assume it was likely, principally, from the volcanoes. If those weren't easily visible, it would be harder to draw conclusions about life, but it would be possible. He pointed out that nitrogen dioxide is normally associated with pollution.

"It's over Los Angeles and Beijing and all of those places because of how the catalysis of exhaust [from cars] works."

When looking for an extraterrestrial civilization, pollution chemicals should be included on the list of "signs" of life, he added. Ozone might also be visible. Fosbury pointed out that at higher latitudes, at the edge of the umbra on the moon, you can see blue.

"It's one of the indicators that there's a lot of ozone," he said.

and finally several upcoming scopes will be able to directly image earth sized planets and then all this preliminary research will come in handy looking for aliens:

Also under construction is the European Extremely Large Telescope (E-ELT), a 39-meter beast that will not only do these velocity measurements, but also image some planets and possibly characterize their atmospheres. This research will come in handy when the E-ELT and NASA's James Webb Space Telescope are working.

Read more at: phys.org...

this article also didn't mention other techniques for seeing signs of exobiology but there are some other ideas out there too.

a reply to: stormbringer1701

So other than the article. What is your opinion on the matter? I skimmed it because honestly this is more of an opinion oriented topic. Oh and I don't know why but the article did say Antarctica only had 1 volcano but in reality is has somewhere around seven.

a reply to: stormbringer1701

When looking for an extraterrestrial civilization, pollution chemicals should be included on the list of "signs" of life, he added.

Polluting the Earth on a grand scale has only been conducted by humans in the past 100 years or so. I would hope and expect that in less than another 100 years we would not be polluting at all. So that's just 200 years in Earth's 4.5 billion year history where we have created enough pollutants for them to be detected in our atmosphere by a 'probe'.

So using Earth as an example, I believe that searching for signs of pollution on exoplanets would largely be a futile experiment.

With a big enough mirror and lensing - one could see almost anything.

So what if they could, unless they had light speed travel, the closest likly candidates would be many many years from us. If they wanted resources there are probably hundreds if not thousands of worlds with plenty of stuff between us (also many asteroids just floating about with major amounts of raw metals and other fancy frozen elements).

originally posted by: Wanderer777
a reply to: stormbringer1701

So other than the article. What is your opinion on the matter? I skimmed it because honestly this is more of an opinion oriented topic. Oh and I don't know why but the article did say Antarctica only had 1 volcano but in reality is has somewhere around seven.

my opinion is based on this and other articles about techniques for finding and analyzing planets. i think we are within a few years of being able to at least get three pixels worth of images of terrestrial sized planets and you can tell a lot more than you can think from just three pixels.

and there is more that is decyperable than just the things in this article. potentially even seeing oceans clouds, ice cover and even city lights or wildfires.

originally posted by: vonspurter
a reply to: stormbringer1701

When looking for an extraterrestrial civilization, pollution chemicals should be included on the list of "signs" of life, he added.

Polluting the Earth on a grand scale has only been conducted by humans in the past 100 years or so. I would hope and expect that in less than another 100 years we would not be polluting at all. So that's just 200 years in Earth's 4.5 billion year history where we have created enough pollutants for them to be detected in our atmosphere by a 'probe'.

So using Earth as an example, I believe that searching for signs of pollution on exoplanets would largely be a futile experiment.

well there are also natural biomarker chemicals and basic geography or cartography. and even the potential to see signs of cities and such. It's not just about pollution. and i agree that if we develop fusion or hydrogen tech our polluting days will be just about over. but it's useful to know how to look for pollution none the less.

a reply to: stormbringer1701
Then you should have put that in the OP. Pet peeve of mine. All people do nowadays is post an article and that is it. No insight or anything. We come here for other members thoughts and opinions on what is going on in the world. If I just wanted to read an article I could go anywhere.

originally posted by: Wanderer777
a reply to: stormbringer1701
Then you should have put that in the OP. Pet peeve of mine. All people do nowadays is post an article and that is it. No insight or anything. We come here for other members thoughts and opinions on what is going on in the world. If I just wanted to read an article I could go anywhere.

i am pretty sure i have discussed all these other things in other peoples threads about exo planets. it's not like i haven't mentioned them. but this article is new the paint is still wet on it. and this is what it was about.

Then post this in those threads. All I'm saying is that if you're going to make a thread then put actual effort into it. Anyone can post an article and it doesn't make it special. Why don't you get multiple articles on the subject and write about them in your own words and put some actual work into it.

a reply to: stormbringer1701

If the ones on the other side are silicon based lifeforms + "at our level of intelligence" they'll look at us and say NO LIFE, it's a barren wasteland not fit for "life as we know it". Hmmm... I think I should re-edit "level of intelligence" to "ignorant & sure of themselves like us".

a reply to: stormbringer1701

Post in this thread...not previous ones. Some folks have never read those to be able to relate to what your even referring to. Dont know what you were thinking.

Your thread here was brand new 1st time to some.

originally posted by: mysterioustranger
a reply to: stormbringer1701

Post in this thread...not previous ones. Some folks have never read those to be able to relate to what your even referring to. Dont know what you were thinking.

Your thread here was brand new 1st time to some.

So is that what we do here, repost threads on the same subject just because the previous thread is a few weeks old?

Its not like the older thread dropped off the front page of this forum either.

There's a thread about this already which contains the same and other information and a bunch of response.

I made it like a week ago or so but it is still on this page.

ATS: An Alien View of Earth - How Alien Astronomers Would Know the Earth is Habitable


Great subject anyway. S+F

originally posted by: vonspurter
a reply to: stormbringer1701

When looking for an extraterrestrial civilization, pollution chemicals should be included on the list of "signs" of life, he added.

Polluting the Earth on a grand scale has only been conducted by humans in the past 100 years or so. I would hope and expect that in less than another 100 years we would not be polluting at all. So that's just 200 years in Earth's 4.5 billion year history where we have created enough pollutants for them to be detected in our atmosphere by a 'probe'.

So using Earth as an example, I believe that searching for signs of pollution on exoplanets would largely be a futile experiment.

One can also easily imagine the opposite scenario of that which you outlined.

It's one which we've seen in dystopian Sci-Fi from Blade Runner, through the Terminator to Elysium.

What if we don't turn Earth into some new garden of eden in 200 years?

What if instead we enter a post-human or trans-human type of existence? When intelligence is free from biological constraints what happens then?

Does pollution matter to androids and cyborgs?

There could be whole planets of nothing but machines creating things like nitrogen dioxide as a byproduct of industrial processes.

When we start to confine the search for extraterrestrial intelligence to that which we deem 'likely' instead of focus on that which is detectable then we've already made a HUGE mistake.

Remember, many astronomers didn't look for "Hot Jupiters" because everyone assumed Jupiters could not orbit close to their star. After all they don't in OUR solar system right?

So what was the first type of exoplanet we detected around a normal star? A Hot Jupiter orbiting the Sunlike star 51 Pegasi.

Our existence is but one example of a planetary system which produced life and intelligence. It is by no means the only one.

Don't look for what is 'likely' look for what is detectable.

originally posted by: Wanderer777
a reply to: stormbringer1701
Then you should have put that in the OP. Pet peeve of mine. All people do nowadays is post an article and that is it. No insight or anything.

That's not true.

Read my original thread on the same subject posted about a month ago if you want some insight.

originally posted by: Wanderer777
Then post this in those threads. All I'm saying is that if you're going to make a thread then put actual effort into it. Anyone can post an article and it doesn't make it special. Why don't you get multiple articles on the subject and write about them in your own words and put some actual work into it.

Kudos for the recommendation to use existing threads on the same subject rather than just starting a new one.