----------------------------------------------------------------------------------------

No atmo means no liquid water, right?
No liquid water means no earth-like (life-as-we-know-it) planet...
Bummmmmer!

Oh well, better luck next time...

--------------------------------------------
On Sun, 2/26/17, Jerry Barrington <xxxxxx@gmail.com> wrote:
 Date: Sunday, February 26, 2017, 12:19 AM

 One of the
 articles I read on Trappist points out that the stellar
 flares associated with such stars likely stripped away any
 atmosphere anyway.
 On Sat, Feb 25, 2017 at
 5:40 PM, Bruce  Johnson <xxxxxx@pharmacy.arizona.edu>
 wrote:

 > On Feb 25, 2017, at 1:21 PM, Phil Pugliese (via tml
 list) <xxxxxx@simplelists.com>
 wrote:

 >

 >

 > I just saw some animations of TRAPPIST-1 on a network
 news prg & it showed all seven planets alongside the
 Earth.

 >

 > All of them appear to be smaller than the Earth.

 Per the Nature article their radii vary from 1.13 to
 .72 times Earth’s, so the animation was wrong.

 <http://dbdev2.pharmacy.
 arizona.edu/miscjunk/ nature21360.pdf> See Table 1.
 Radius is expressed as ratio to Earth’s.

 >

 > Made me wonder if any of those planets could maintain a
 breathable atmo.

 > How much smaller could a planet otherwise similar to
 Earth be & still have an atmo thick enough for us to
 breathe w/o assist?

 > (I imagine a Venus-size planet could. But could a
 Mars-sized one?)

 Mars lost it’s atmosphere largely because it has a
 cold iron non-spinning core, meaning no magnetic field, and
 so the solar wind pretty much blew away the atmosphere over
 time. We know that Mars had enough atmosphere at one point
 to have considerable liquid running on the surface. Titan is
 only .4 the diameter of Earth, smaller than Mars, but
 atmospheric pressure on the surface is almost one and a half
 times Earths.

 --

 Bruce Johnson

 University of Arizona

 College of Pharmacy

 Information Technology Group

 Institutions do not have opinions, merely customs

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