Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO389.TXT

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Date: Sat,  7 Nov 92 05:02:10
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #389
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat,  7 Nov 92       Volume 15 : Issue 389

Today's Topics:
              "Earth Gains a Retinue of Mini-Asteroids"
          ANSWER: Recognizing a Dyson sphere if you saw one
                 Automated space station construction
                             clarke's law
                   Coverup - gravity doesn't exist?
                  Hubble's mirror  or Really Costar.
            Making up nonsense (was Re: Man in space ... )
                           Man in space ...
                        NASA Coverup (7 msgs)
                       Nuclear waste to Venus?
                            Slush Hydrogen
              Viking Photos Shows Evidence of Marsquakes

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

Date: Fri, 6 Nov 1992 08:17:01 GMT
From: Dan Tilque <[e-mail]>
Subject: "Earth Gains a Retinue of Mini-Asteroids"
Newsgroups: sci.astro,sci.space

[e-mail] (Jim Scotti x2717) writes:
>[e-mail] (Paul Dietz) writes:
>>
>>Since the Tunguska event is thought to have been due to a 40 meter
>>body, and such events were calculated to occur once every 2 to 3
>>centuries, something is screwy here.
>
>Not really screwy.  The number of 50 meter objects is enhanced by
>about 10 times and the Tunguska type events probably happen once
>or a few times per century.

This sparked a memory, but unfortunately not a detailed one.

There was a second (but less powerful) Siberian meteor-explosion
sometime after Tunguska.  I seem to remember that it was in either the
20's or the 40's, but the name of it totally eludes me.

Anyone know about this?

---
Dan Tilque    --     [e-mail]

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

Date: 6 Nov 92 17:32:23 GMT
From: Erik Max Francis <[e-mail]>
Subject: ANSWER: Recognizing a Dyson sphere if you saw one
Newsgroups: sci.astro,sci.space

[e-mail] (Frederick A. Ringwald) writes:

> No - the main point to the article is that the filling factor does not
> necessarily have to be high, so plenty of light from the central star
> would get through. What we'd see is a Sun-like star, with a small IR
> excess indicating a 300 K shell with size on the order of 1 AU: in
> other words, something not necessarily easily distinguishable from a
> natural object. Unless there's something obvious, such as narrow-band
> radio signals...

Oh.  So you're assuming that the Dyson sphere would be semitransparent?
Sounds then like it would look like an F-K shell star . . .

----------
Erik Max Francis   Omnia quia sunt, lumina sunt.  Coming soon:  UNIVERSE _ | _
USmail:  1070 Oakmont Dr. #1 San Jose CA 95117  ICBM:  37 20 N  121 53 W _>|<_
UUCP:  ..!apple!uuwest!max   Usenet:  [e-mail]   464E4F5244   |

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

Date: Fri, 6 Nov 1992 16:04:47 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Automated space station construction
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (David Rowland) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
[Glad bag plant story deleted]
>>
>>The moral of this story is that robotics is not yet adaptive enough to
>>unexpected conditions to operate without waste and possible harm in less
>>than critically supervised operations.
>
>But wouldn't the robots been discussed here be operated remotely by
>ground based people.  This way, there is no need to program much AI
>into the system.

That isn't robotics, it's teleoperation. That's available now. The
Shuttle has the Canadarm and so will Freedom. They're operated on
site because the maximum 7 second communications delay through the
relay satellites is too much for real time assembly from the ground.
Robots have autonomy, at least of a limited kind. They have to respond
in real time to real time events. My example about the bag plant was
to show that unforeseen  things still come up in well understood
environments. A robot can't react to a stimulus it isn't programmed
to recognize as a problem.

I expect that improvements in routing statellite communications could
get the average control lag down to under 1.5 seconds. That would help
a lot. However, the lag is constantly changing due to the low Earth
orbit so I'd expect it to be a nightmare for the operator to compensate.
I also expect that as we gain more experience in space assembly, we'll
know what kinds of problems are likely to occur and can program a robot
to recognize them and react properly. That's likely to be one of the
lessons learned from Freedom assembly.

Gary

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

From: Thomas Clarke <[e-mail]>
Subject: clarke's law
Newsgroups: sci.space,sci.astro,sci.physics.fusion

Sender: News system <[e-mail]>
Organization: University of Central Florida
Date: Wed, 4 Nov 1992 22:03:19 GMT
Lines: 15
Source-Info:  Sender is really [e-mail]
Source-Info:  Sender is really [e-mail]

Someone recently posted Clarke's law.  The one about
if a senior scientist says possible he's probably right,
if he says impossible he's probably wrong.

Could you e-mail me the exact quotation?  I need to cite it
in a paper and don't want to go digging in the library.

Thanks.
--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
[phone], FAX: [phone], [e-mail]

no relation

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

Date: 6 Nov 92 18:03:00 GMT
From: Roger Wilfong <[e-mail]>
Subject: Coverup - gravity doesn't exist?
Newsgroups: sci.space

In Article <[e-mail]> "[e-mail] (John Roberts)" says:
>
> -From: [e-mail] (Peter J. Scott)
> -Subject: Re: NASA Coverup
> -Date: 5 Nov 92 18:24:25 GMT
> -Organization: Jet Propulsion Laboratory, NASA/Caltech
>
> -Ah, but have you personally verified Newton's Law of Gravitation?  After
> -all, who do you think started this whole conspiracy?  Can any of us say
> -that we really knew Isaac Newton?
>
> *I* haven't, but my roommate in college did. He was a pretty honest fellow,
> so I expect he was telling the truth about the results.
>
> There's an apple tree on the NIST grounds that's a direct descendant of the
> tree Isaac Newton was sitting under when he thought up the laws of gravitation.
> I suppose we could set up a video camera and determine whether there's
> anything unusual about the trajectory of the apples falling from that
> particular tree. If they just float in midair or gently drift to the ground,
> then there's reason to suspect that Isaac made the whole thing up.
>
> :-)
>

There's always Alway's Speculation on Physical Laws.

   "Until a physical law is discovered, compliance is not mandatory."

It's kind of like "if a tree fell in the woods ...".  As applied to gravity,
Alway's Speculation is that before Newton, objects fell because they wanted
too (but when no one was looking, they sometimes fell up) - after Newton,
objects were required to fall under force of law (a force much greater than
gravity).
:-)

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

Date: 6 Nov 92 21:33:39 GMT
From: _Floor_ <[e-mail]>
Subject: Hubble's mirror  or Really Costar.
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
] As for an annoying problem, the South Atlantic Anomaly and flapping of
] the solar arrays give a lot more headaches around here than solar avoidance.
]
] -Bill Gawne,  Space Telescope Science Institute

What is the South Atlantic Anomaly?

  _____    "But you can't really call that a dance. It's a walk." - Tony Banks
 /  ___\  ___  __ ___   ___      _____________   [e-mail]
 | / __  / _ \ | /   \ / _ \     |  physics  |   [e-mail]
 | \_\ \ | __/ |  /\ | | __/     |racquetball|   [e-mail]
 \_____/ \___/ |_| |_| \___/     |volleyball |   [e-mail]
 Gene Van Buren, Kzoo Crew(Floor), Washington U. in St. Lou - #1 in Volleyball

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

Date: Fri, 6 Nov 1992 21:52:09 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: Making up nonsense (was Re: Man in space ... )
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Edward V. Wright) writes:
> In <[e-mail]> [e-mail] (Andrew Haveland-Robinson) writes:
[reference to orginal posting has been lost.  It's denoted by ">>>" here.]
>>>   What will happen if the space suite of an austronaut gets ripped
>>>in space ?
>>>   Some of us recon that he will explode while others that he will end up
>>>with lots of bruises!!. One thing that all of us agree, is that it is not
>>>going to be a very healthy activity.
>
>>Well Nick, my feeling is that he would nearly explode.
>
> Well, Andrew, it's like this.  The universe just doesn't care how
> you *feel*.
>
[explanation of what really happens deleted]

> All of this information has been publicly available for *decades.*
> So why do self-styled experts keep making up absolute nonsense
> instead of just reading the relevent literature?

Actually you have three choices:

1. Make up absolute nonsense.
2. Read the relevant literature.
3. Ask the readers of Usenet.

Choice 3 is not always appropriate, especially when 2 is available in
an almanac or encyclopedia.  In this case it wasn't a bad idea, but I
told Nick to use the fourth option:

4. Check the sci.space FAQ to see if the question is answered there.

As for Andy, I suppose he took what he knew about physics and biology
and speculated about the answer.  That doesn't seem to deserve Ed's
nasty tone... or does it?  You're allowed to be wrong around here, but
you have to put up with the kidding. E.g.:

Evidently Andy has seen *Total Recall* but not *2001*, or, if he's
seen both, he believes the former has more accurate science than the
latter.

Bill Higgins, Beam Jockey              | Comet Swift-Tuttle is
Fermi National Accelerator Laboratory  | Mama Nature's way of
Bitnet:           [e-mail]  | saying it's time to
Internet:       [e-mail]  | get off the planet.
SPAN/Hepnet:           43011::HIGGINS  |   --Dale Amon

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

Date: 6 Nov 92 19:59:33 GMT
From: "Edward V. Wright" <[e-mail]>
Subject: Man in space ...
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Andrew Haveland-Robinson) writes:

>>   What will happen if the space suite of an austronaut gets ripped
>>in space ?
>>   Some of us recon that he will explode while others that he will end up
>>with lots of bruises!!. One thing that all of us agree, is that it is not
>>going to be a very healthy activity.

>Well Nick, my feeling is that he would nearly explode.

Well, Andrew, it's like this.  The universe just doesn't care how
you *feel*.

That's why scientists rely on *experiments* rather than feelings.
NASA and the US Air Force did numerous experiments, involving dogs
and chimpanzees, during the 1960's.  None of the animals exploded.
Their lungs didn't rupture.  Their windpipes didn't "lock."  Their
eyes didn't pop out and they didn't die of an "instant and massive
stroke."  In fact, the animals were able to retain conciousness for
30-60 seconds and usually (except from a few animals that contracted
the bends and had to be destroyed) recovered with no irreversible harm.

All of this information has been publicly available for *decades.*
So why do self-styled experts keep making up absolute nonsense
instead of just reading the relevent literature?

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

Date: Fri, 6 Nov 1992 16:49:19 GMT
From: Gary Coffman <ke4zv!gary>
Subject: NASA Coverup
Newsgroups: alt.conspiracy,sci.space

In article <[e-mail]> [e-mail] writes:
>
>   Dillon Pyron writes:
>  > To  the point.  Your calculations assume that the earth and moon have the
>  > same density, and that it is homogenous.
>
>   Which body does your pronoun "it" refer to ?  My  calculations are  taken
>   right  out  of  Abell's  pre- Apollo  astronomy  text "Exploration of the
>   Universe" (Holt Reinhart, 1964) and Beiser's "Physics" (Cummings) ,1973.
>
>   Beiser states , on page 118 , "A spherical object behaves  gravitationally
>   as  if  it's  mass  were concentrated at it's center" . He also states,on
>   page 119, that  the  earth's  gravitational  pull  on  an  object  varies
>   inversely  with the square of it's distance FROM THE CENTER OF THE EARTH.
>   I also assume that a similar rule applies to the moon.

It doesn't even apply to the Earth. One of the things learned from early
satellite launches is that the Earth, and to an even greater extent the
Moon, have what are called mascons, mass concentrations. These are unevenly
distributed areas of higher density inside the body. Beiser's assumption
holds up as a close approximation when the two bodies are far enough
apart that their radius is an insignificant part of their separation
distance, say Earth-Sun distance. But they fail miserably when the
separation is less than a few body radiuses. The mascons will warp the
orbit of the satellite a measurable amount. That's what the Magellan
space probe is doing right now, a gravity map of Venus using the perturbations
of the satellite's orbit as it passes over varying density material in
the planet below. The existance of tides is a direct result of the effect
of differentials in gravitational potential across the diameter of a
body. Using Beiser's simplifing assumption, there could be no tides on
Earth. Since we can easily observe that there are, his assumption is
invalid for bodies as close together as the Earth and the Moon.

The other assumption Beiser uses is that of spherical objects. Neither
the Earth nor the Moon are spheres. The Earth is an oblate spheriod, and
the Moon is somewhat pear shaped with the greatest mass on the side facing
Earth. This is again significant when the separation distance is a few
planetary radiuses.

The most damning evidence against your theory that the Moon has a
gravity of .6 G is that we know the orbital period of the Moon to
a great accuracy, and we know the mass of the Earth and the distance
to the Moon. With those three numbers, we can calculate exactly how
much centrifigual force is in the system, and thus how much gravitational
force is required to counterbalance it. So if the Moon stays in orbit,
and it does, we can state it's gravitational pull to a high degree of
accuracy.

Gary

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

Date: Fri, 6 Nov 1992 18:57:47 GMT
From: Paul Dietz <[e-mail]>
Subject: Nasa Coverup
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:

> I mentioned Paul Dietz: he is part of our community here, and is a
> very respected part of it at that. If he is not busy with life outside
> of cyberspace, I'm sure he could address what you have said, and far
> better than most of us. If he is listening in now, it is up to him.

Oh, good grief.  This snarfy person is either a leg-puller or a
clueless, paranoid buffoon.  I am surprised Henry made even one reply.
The suggestion that Apollo was faked is just too much for any sane,
moderately informed person to believe.

    Paul

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

Date: 6 Nov 92 16:25:19 GMT
From: Gary Coffman <ke4zv!gary>
Subject: NASA Coverup
Newsgroups: sci.physics,sci.space

In article <[e-mail]> [e-mail] (Bill Higgins-- Beam Jockey) writes:
>In article <[e-mail]>, [e-mail] () writes:
>>
>> Monday night on PBS, there was a special on Space Exploration which showed an
>> interesting experiment.  One of the astronauts dropped a hammer and feather
>> at the same time to show that Galieo was right.
>[...]
>
>Hidden assumption:  this film is playing back on your TV set at the
>same speed it was photographed.  (Or is it video?)  In any case, you
>need to know the correct frame rate to get an accurate value for t, and
>even then you will have some irreducible error in the measurement,
>thanks to the discrete time resolution of film and video.

I remember this. It was *live* video from the moon. I was working the
late shift at CBS when it came in. I know we made a quad tape of it.
The field rate of NTSC limits time resolution to 1/60th second, but
that's certainly sufficient to tell the difference between .6 G and
.166 G.

Gary

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

Date: 6 Nov 92 19:13:42 GMT
From: Curtis Roelle <roelle@uars_mag.jhuapl.edu>
Subject: NASA Coverup
Newsgroups: alt.conspiracy,sci.space

An R&D electronics techniciann (a.k.a [e-mail]) writes:

>   Also,  I  note that someone on the net has viewed a video of an astronaut
>   on the moon dropping a hammer and a feather  simultaneously.  This  video
>   would  be extremely pertinent in proving or disproving my allegations. If
>   we knew the approximate height and fall times of  the  objects,  assuming
>   the  video  was  played back in real time, we'd know the acceleration,and
>   the argument would be over.

The astronaut was Apollo 14 Commander Alan Sheppard (also the first
U.S.  citizen in space).  He conducted several simple experiments
during lunar EVA including hitting a golf ball.  I recall watching it
live: he took quite a swing then had trouble regaining his balance in
the "thin" lunar gravity.  His forsight in conducting simple science
experiments on the moon have convinced me Shappard anticipated that
the present conspiracy theory would eventually be discussed :-).

BTW, a long-running exhibit at the SASM has a t.v. monitor that
continuously plays video footage from the Apollo moonwalks, including
astronauts (in full 250-lb moonsuits) giving the American flag leaping
salutes, and skidding around the dust in the lunar rover.  Perhaps
the lunar gravity question can be put to rest by timing how long it
takes dust thrown up by the lunar rover to settle :-) ?

Curt Roelle

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

Date: Fri, 6 Nov 1992 19:01:02 GMT
From: Ed McCreary <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space,alt.conspiracy

In article <[e-mail]> [e-mail] (Tom Nugent       ) writes:
>[e-mail] writes:
>
>>    Ranger  6,  launched on January 30th 1964, allegedly had it's electrical
>>   system burn out in flight and no pictures were sent.   Subsequent  Ranger
>>   Probes  were  more  successful  .
>
>I thought that the reason Ranger 6 didn't send back pictures was because
>they forgot to take off the 'lens cap' before launch.  Seriously.  That's
>why they now have little red tags all over new probes etc. which say "Remove
>before launch."  At least that's the story I heard from a JPL engineer.
>

Hmm, the references I have say that the TV power supply shorted out
during booster separation.


--
====
Ed McCreary                                               ,__o
[e-mail]                       _-\_<,
"If it were not for laughter, there would be no Tao."  (*)/'(*)

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

Date: Fri, 6 Nov 1992 20:28:31 GMT
From: "Michael K. Heney" <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.physics,sci.space,alt.conspiracy

In article <[e-mail]> [e-mail] (Fran Litterio) writes:
>
> [...]
>
>Then the was the time an astronaut caught his foot on a cable and
>knocked over a rack of million dollar equipment.  It was useless
>thereafter (anyone know who did that?).  I guess I shouldn't feel so
>bad about getting crumbs in my keyboard.

That was John Young, and he ended up breaking a wire which rendered
the experiment useless.  I used to share an office with a guy who used
to work at Bendix in Ann Arbor, and this was one of his favorite stories.
A few Bendix engineers worked late into the night on a fix.  Their
proposal - strip the insulation off with Ye Olde Swiss Army Knife,
lay the bared wires one atop the other, and put a rock on it!  The main
reason they didn't try this was impact on their time line.  (I have
a feeling that messing with a knife in spacesuits was a bit of a concern
as well ...)


--
Mike Heney                |   Senior Systems Analyst and     |  Reach for the
[e-mail]   |  Space Activist / Entrepreneur   |  Stars, eh?
Kensington, MD (near DC)  |     * Will Work for Money *      |

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

Date: 6 Nov 92 22:57:55 GMT
From: Patrick Chester <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space,alt.conspiracy

In article <[e-mail]> [e-mail] writes:
[
[   I'm not trying to suggest that we didn't land on (and  return  from)  the
[   moon. What I doubt is that we could have done it all with rockets.

Do you know some B.A. in Physics and Astronomy named Robert McElwaine?
Why couldn't rockets be used? The gravity you claim is still less than
one gee and there is no atmosphere to claw through on the way up.

[
[ >  Also  remember  that the Astronauts suits and baggage were set up for 1/6
[ >  g and not .6 gee.
[
[   So  we  made  them extra heavy so the astronauts couldn't jump too high ,
[   or wander off too far, right ? (see my most recent post.)

The suits (as noted in an earlier post by someone else) were heavy because of
the material and equipment required for them. They might have been able to
make suits that were lighter but that would have required removing a bit of
safety margin. Say, less life support maybe? How about a slightly thinner suit?

[  > If any of you out there know Buzz Aldrin, there is no way he  would  keep
[  > something like this covered up.
[
[   Probably not , sorry , gee, I guess you're right . Do you think there's a
[   chance I might get to talk with your good buddy Buzz? Over the ol' modem?
[   Us investigative types just like to get told off by those in  a  position
[   to know , y'know ?

I thought you said everyone "in the know" was a conspirator. Or words to that
effect.

[
[  >So there snarfy.
[
[   Yeah , don't rub it in O.K.?  I'm very sensitive.
[
[   Now  that  you  mention Buzz Aldrin, didn't I read somewhere that he went
[   through severe depression and "therapy" after  his  one  moon  excursion?
[   What  was  this all about?  Was he confused or upset about anything after
[   this experience?

I think he was treated a few years after his lunar mission. Not immediately
after it.

I think he was depressed because we went to the Moon six times and then stopped
completely and fiddled around. Still doing it too. I know the idea depresses
me.

[
[   snarfy


--
Patrick Chester            |----------------------------------------------------
[e-mail] |"The earth is too fragile a basket in which to keep
Politically Incorrect      |  all your eggs." Robert A. Heinlein
Future Lunar Colonist      |"The meek shall inherit the Earth. The rest of us
#^%$!! Militarist          |  are going to the stars." Anonymous
(Of the Sun Tzu mentality) |----------------------------------------------------

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

Date: Fri, 6 Nov 92 23:25:40 GMT
From: Steven Reardon <[e-mail]>
Subject: Nuclear waste to Venus?
Newsgroups: sci.space

In <[e-mail]> [e-mail] (John Roberts) writes:

>-HS>Venus, you might as well just fly it *into* Venus.  It's not as if Venus
>-HS>is good for anything else.  (Although one would want to do rather more
>-HS>thorough studies of Venus before starting to use it as a dump...)

>-Why do that?  Conceivably Venusian terraforming could be done and now
>-you've contaminated it with radioactives.  If dumping is the solution
>-dump on an airless body.

>Without working too hard at the math, I strongly suspect that cleaning up
>a few million tons of high-level radioactive waste would add far less than
>a thousandth of a percent to the cost of terraforming Venus. With that kind
>of cost ratio, it would be an insignificant impediment to terraforming.

>This is not to say I favor the idea - I think the nuclear waste should be
>kept on the Earth.

Say, if you're gonna get it going fast enough to escape Earth, why not just
aim it at the sun?  It would disintigrate long before it got there.

Just my 2 hunks of crust worth,

Steve

--
*   The state has a system set up whereby the only people who are       *
*   allowed to have guns are those without convictions.                 *
*  ---                                              --- Steven Reardon  *
*"Gun Control" is hitting your target. ** [e-mail]  *

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

Date: Fri, 6 Nov 1992 18:50:17 GMT
From: Jordin Kare <[e-mail]>
Subject: Slush Hydrogen
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Jeff Greason ~) writes:
>
>What exactly is "slush hydrogen?"

    It's the stuff that covers the sidewalks after a
snowstorm on Jupiter :-)

    Jordin Kare

--

    Jordin Kare    [e-mail]    510-426-0363

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

Date: Sat, 7 Nov 1992 07:40:54 GMT
From: Ron Baalke <[e-mail]>
Subject: Viking Photos Shows Evidence of Marsquakes
Newsgroups: sci.space,sci.astro,alt.sci.planetary,sci.geo.geology

Paula Cleggett-Haleim
Headquarters, Washington, D.C.         November 6, 1992
(Phone:  [phone])

Jim Doyle
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  [phone])

RELEASE:  92-198

VIKING PHOTOS SHOW MARS MAY EXPERIENCE FREQUENT QUAKES

     Mars was once very active tectonically and may still be
shaken by quakes daily, according to scientists using NASA's
Viking Orbiter photos of the red planet's surface.

     In a science paper published today, Drs. Matthew
Golombek, W. Bruce Banerdt and David M. Tralli of the Jet
Propulsion Laboratory and Dr. Kenneth L. Tanaka of the U.S.
Geological Survey said Mars is more seismically active than
the moon, but less so than Earth.

     "Because Mars is smaller than Earth, little more than
half the size, a magnitude 6 quake on Mars would have 10
times the effect it would on Earth," Golombek said.

     Marsquakes of that magnitude may occur about once every
4 and a half years, he said.  A marsquake of about magnitude
4, however, might happen somewhere on the planet once a month
on an average.  Yet, a quake of magnitude 4 would be
detectable throughout the planet, again because of its size
and presumed  structure.

     Tectonic features on Mars are found mostly around the
Tharsis region, a large volcanic plateau with associated
features that cover the entire western hemisphere of the
planet.

     Tectonism in that region occurred mainly during two
periods in the planet's history -- the earliest possibly as
long ago as 4-billion years and the most recent ending
possibly less than one-billion years ago.

     Features that formed during the first seismic period
include many narrow graben or long ditch-like or trough
features with faults along their sides.  Also formed at that
time was a system of concentric wrinkle ridges, larger graben
and rifts, and the deep rift valleys of Mars' great 1,860-
mile-long (3,000-kilometer) canyon, the Valles Marineris.

     During the second period, tectonism caused an enormous
set of radial grabens that extend up to thousands of
kilometers from the center of the plateau and rift zones of
Valles Marineris, along with other prominent features.

     Tectonism and seismic activity have decreased from the
earlier period to the present, Golombek said, as would be
expected if the seismic activity is governed by simple
cooling of the lithosphere -- the rigid outer crust and upper
part of the mantle -- of the planet.

     The scientists said that while Mars is less seismically
active than Earth, their studies predict that about two
marsquakes of magnitude 5 or greater occur per year, about a
hundred quakes of magnitude 3 or greater occur per year.

     "That is a promising prospect for seismological
investigations on future missions to Mars," Golombek said.

     Golombek is the Project Scientist for the Mars
Environmental Survey (MESUR) project which would place a
network of landers, each with a seismometer, in different
locations on the Martian surface.  Recordings of marsquakes
by seismometers at different locations will help determine
the internal structure of the red planet.

     The network of instrumented landers is planned to be
deployed over three Mars launch opportunities.  Four would be
sent in 1999, four more in 2001 and the final eight launched
with four each on two launch vehicles in 2003.

     A precursor mission called MESUR Pathfinder is under
study as part of NASA's proposed Discovery Program of small,
low-cost planetary missions.  MESUR Pathfinder would place a
single lander on Mars with a robotic rover deploying, among
other instruments, a seismometer as early as 1996.

     The paper, published today in Science magazine, is
entitled "A Prediction of Mars Seismicity from Surface
Faulting."

     The Discovery Program and the Viking mission are managed
by NASA's Office of Space Science and Applications, NASA
Headquarters, Washington, D.C.

- end -
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Give people a second
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | chance, but not a third.
|_____|/  |_|/       |_____|/                     |

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End of Space Digest Volume 15 : Issue 389
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