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#1 Re: Life support systems » Eat Like a Martian » 2008-05-28 13:40:56

Why do Metal Halide and Sodium lamps still exist?

High power LEDs (> 1W) are currently more expensive (per lumen), and are a little bit picky about the quality of the power supply you give them - in some areas that means you'd also need a power conditioner.

#2 Re: Interplanetary transportation » Retrorockets in vogue? » 2008-05-28 02:28:23

why wouldn't we?

It is just too tempting to get the 6.4 km/sec delta vee for "free".  The problem is that the mass ratio (inital/payload) is an exponential function of delta vee.  All else being equal, your payload will be reduced by a factor of 1/10 (or your rocket has to be 10 times bigger initially).  You'll always take the aerobrake risk if it's available.  For chemical rockets anyway.

***EDIT to use a more reasonable specific impulse.

#4 Re: Life support systems » Eat Like a Martian » 2008-05-27 22:56:04

I thought you had to use specialized lights giving off certain spectrum's. Can you really use LEDs?

Actually they are quite efficient.  Chlorophyll only responds to these frequencies ...

absorption-spectrum.jpg

... so a two color LED array wastes very little power ...

led_v_fluor.jpg

#5 Re: Not So Free Chat » The American Caesar » 2008-05-27 22:38:38

I'll wait for people's opinions on this subject and then comment further.

Sedition and conspiracy to commit high treason boiling beneath every word.  Go ahead and document your criminal intent here.  It'll make the job of the Black Panther Brigades easier.

(Actually the Democratic party is looking so dysfunctional they'll be lucky to nominate a candidate let alone win the general roll)

#6 Re: Intelligent Alien Life » Artefact on Mars? » 2008-05-27 04:37:45

Hi Major Tom (I love that song), welcome to New Mars.

Speculation has it that the object is the heatshield that separated from the lander during EDL.

#7 Re: Unmanned probes » Phoenix - North Pole Region Lander (PHX) » 2008-05-26 05:38:24

Are the Phoenix cameras going to be monitoring the sky for "weather"?

Yes.  There is also a lidar on board.  A big part of the mission is to observe the seasonal changes into winter.  You'll get some excitement as the lander gets covered in CO2 ice.  It'll be cool if we get to watch the thaw, but the lander will probably die during the winter.

#8 Re: Unmanned probes » Phoenix - North Pole Region Lander (PHX) » 2008-05-25 23:27:27

This is the polygonal terrain they were looking for (similar ice modified terrain occurs in Antarctica)

230117main_false_color_postcard_516-387.jpg

#9 Re: Unmanned probes » Phoenix - North Pole Region Lander (PHX) » 2008-05-25 23:05:05

Preliminary data says the landing site is 68.22 degrees latitude and 234.3 degrees longitude.

You can see where that is using these maps ..

http://planetary.org/blog/article/00001431/

**EDIT

Better estimate of the landing site (68.011 lat, 236.994 long - right at the edge of the 3-sigma ellipse!) ...

PhoenixLandingFirstEstimateNoGrid_800-600_lg.jpg

Here is the closest HiRISE image ...

http://hirise.lpl.arizona.edu/PSP_006930_2480

PSP_006930_2480.jpg

#11 Re: Unmanned probes » Phoenix - North Pole Region Lander (PHX) » 2008-05-25 21:34:50

Raw images available from ...

http://fawkes4.lpl.arizona.edu/images.php?gID=0&cID=7

The solar panels are fully deployed, so we are off and running.

Congrats to the Phoenix Mission Team!

#12 Re: Not So Free Chat » Did Iran become a player in space ? » 2008-05-25 12:44:32

I can't believe I'm saying this, but....

Democracy isn't always the best form of government, not if it means dictatorship of the majority.

What!?  Minorities have rights?  That's quite a big step for you Terraformer.  Careful though, next you'll be imagining what your life would have been like if you'd been born into a minority, and we all know where that leads.

#13 Re: Pictures of Mars » THE PAST MARS : Noachian & Hesperian » 2008-05-24 18:14:01

I created a texture of the ancient surface of Mars in the Noachian era.

Très chic.

Here's first image, you never saw it?

No - thank you for making it.

The next, I will add the some lava and the clouds in this texture soon.

I'll look forward to that.

#14 Re: Human missions » International Space Station (ISS / Alpha) » 2008-05-22 21:34:03

The Soyuz TMA-11 ballistic re-entry was caused by the failure of the equipment bay to detach ...

http://abcnews.go.com/Technology/story?id=4901625

#16 Re: Interplanetary transportation » Relativity of light - light at light speed » 2008-05-14 21:50:51

I've often wondered what it was about quantum theory that Eistein didn't understand....

Einstein understood Quantum theory very well.  He just didn't like the implications.  In particular that Bell's Theorem ...

http://en.wikipedia.org/wiki/Bell%27s_Theorem

... requires that we abandon locality (allow "spooky action at a distance") or counterfactual definiteness (things exist even when you're not looking at them).  Most physicists choose to abandon locality, but Einstein didn't want to give up either - and who can blame him?

#17 Re: Science, Technology, and Astronomy » Titan » 2008-05-12 10:05:24

You certainly have an eye for beauty, Vincent.

#18 Re: Intelligent Alien Life » Why No Contact Yet ? » 2008-05-11 00:37:07

Here is an article that talks about how far out TV signals may be detectable ...

Aliens Can Watch `I Love Lucy', Lou Scheffer
http://contactincontext.org/cic/v2i1/lucy.htm

Here is a web calculator for other types of signals ...

SETI Range Calculator, Eric Johnston
http://www.satsig.net/seticalc.htm

Note that we think that _very_ large "virtual dishes" can be constructed using  VLBI techniques ...

http://en.wikipedia.org/wiki/VLBI

#19 Re: Water on Mars » Color of the ocean under Noachian » 2008-05-10 07:26:19

Hi PeterC, welcome to New Mars.

In the Noachian period, the water was alkaline, like early Earth.  Lots of clay was deposited.

But in the Hesperian period, the water was acid.  Then the ocean was a wonderful turquoise ...

copahue1.JPG

http://www.wesleyan.edu/ees/JCV/vlsa1.html

#20 Re: Science, Technology, and Astronomy » ID is the best theory at the moment. » 2008-05-09 23:50:08

ID basically is the TOE with the implication that there is a greater purpose behind the forces that drive it.

Is it really?  Isn't a God of the Gaps even less satisfying that Creationism?  At least "Let there be light" has poetry.  This whole "scientists can't explain that, so God did it" and then, when science explains that, "well ... you still can't explain this different thing, so God did it instead."  I mean it is just embarrassing.  They are shooting themselves in the foot by making God just another name for ignorance.

#21 Re: Intelligent Alien Life » Why No Contact Yet ? » 2008-05-09 23:35:01

The 1,000 would be an upper bound.  One thousand or less.

1000 doesn't seem unreasonable for worlds of origin.  But if you've got a million years up your sleeve and tech at the level of star lifting ( http://en.wikipedia.org/wiki/Star_lifting ), I don't see what's stopping you from colonizing the vast majority of stars.

#22 Re: Intelligent Alien Life » Why No Contact Yet ? » 2008-05-09 23:30:34

Can we use that same sort of formula for colonizing to other galaxies?

You can use the same formula, but you run up against a pretty important limit - the age of the universe.

It's that first figure that is the kicker.  On average, galaxies are 1 million light-years apart.  So travel times alone could easily be on the order of 10 million years.  But suppose that 1% of populated galaxies colonize a new galaxy every 10 million years.  Then, you'd need 25 billion years (and that's not even counting dark matter galaxies http://en.wikipedia.org/wiki/Dark_galaxy ).  But the estimated age of the universe is 14 billion years, so even if some civilization began an intergalactic colonization program soon after the big bang, they'd still only have colonized 1 in a million galaxies.  And if life didn't arise anywhere until, say, 8 billion years ago (after supernovas had some time to create the heavier elements) then they'd have colonized only 1000 galaxies. 

The distances are truly immense to get to the closest other galaxy for any species from any galaxy.

That might be the ultimate barrier, even with very fast travel and very long lived species the distance will still be daunting.

On those timescales though, who can know?  I mean, 100 years ago, it was thought impossible to travel in a vacuum because there'd be nothing to push on.

#24 Re: Intelligent Alien Life » Why No Contact Yet ? » 2008-05-08 17:19:50

even if it is slow, every possible star should have been colonized by now:

This is exactly what Fermi pointed out in 1950.

Yes indeed.  But this seems to suggest a higher lower bound on the chance that a random star system is inhabited. 

Doesn't your figure suggest that there are only (400e9)(1/400e6) = 1000 habitable star systems?

#25 Re: Intelligent Alien Life » Why No Contact Yet ? » 2008-05-08 15:36:51

To put it another way, the chance of an advanced ET associated with any given star system must be greater than about 1 to 400 million

However, if you don't assume that interstellar travel is impossible, then even if it is slow, every possible star should have been colonized by now:

- suppose it takes 10,000 years to colonize just one other star system
- suppose only 1% of newly colonized star systems ever colonize another star system
- then the number of colonized star systems will double every 700,000 years or so (by compound interest).
- but it only takes 40 doublings to go from 1 to 1 trillion
- so every possible star system in our galaxy will have been colonized within 28,000,000 years
- which is the blink of an eye, geologically speaking.

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