Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V12_4/V12_476.TXT

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Subject: SPACE Digest V12 #476

SPACE Digest                                     Volume 12 : Issue 476

Today's Topics:
              Re: Deep Lunar Dust Story?
             Re: Theories needed on life
            Deep Lunar Dust Story?
              Re: SPACE Digest V12 #464
             Ulysses Update #2 - 10/19/90
             Re: Theories needed on life
              Re: Venus/Magellan, poles

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription notices,
  should be sent to [e-mail], or, if urgent, to
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----------------------------------------------------------------------

Date: 19 Oct 90 15:19:06 GMT
From: ubc-cs!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Deep Lunar Dust Story?

In article <[e-mail]> [e-mail] (Nichael Cramer) writes:
>    ... Actually, Australian radio physicists,
>    working on 24,000 Mc/s, have already got about a meter inside the Moon!
>    They have shown that the dust layer is probably only about 1mm thick,
>    with solid rock underneath...

And of course, they were wrong, since the lunar regolith is quite a bit
more than 1mm thick.  Solid rock is a long way down; the surface layer
has been churned to dust and fragments by meteorite bombardment.
--
The type syntax for C is essentially   | Henry Spencer at U of Toronto Zoology
unparsable.             --Rob Pike     |  [e-mail]   utzoo!henry

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

Date: 20 Oct 90 15:58:41 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Theories needed on life

In article <[e-mail]> [e-mail] (Mike Gobbi) writes:
>
>A planet 3 or 4 times the size of earth?  Do you mean 3xmass or 3xradius?
>
>In the former case, I suspect that the life forms would have short thick
>legs, and would be unlikely to be humanoid.  Far more likely, they would have
>four or more legs to distribute their mass.
>
>In the latter case, we are talking about a 27-G planet!
>
   Not at all! If we assume that the mean density remains constant,
tripling the radius triples the surface gravity. Tripling the mass
raises the surface gravity by a factor of 3^(1/3) which is roughly a 44%
increase.
   I don't see that a 44% higher gravity is completely outside the realm
of humanoid shape. Birds might be a bit huskier, though  :-)


--
 Christopher Neufeld....Just a graduate student  | "The pizza was just a
 [e-mail]    Ad astra! | detonator; I mean, if
 cneufeld@{pnet91,pro-micol}.cts.com             | it had set off the
 "Don't edit reality for the sake of simplicity" | hams...." Downtown Brown

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

Date: 19 Oct 90 07:55:30 GMT
From: bbn.com![e-mail]  (Nichael Cramer)
Subject: Deep Lunar Dust Story?


A couple of weeks back on Sci.Physics someone [sorry, can't seem to find
the original posting] recounted the "NASA was concerned that the
lunar-lander might sink in the deep moondust" story.

On the other hand, I recently came across the following (in _Astounding
Days_, the second volume of Arthur C. Clarke's "autobiography").  It is
from a letter by ACC that was published in in the Dec 1950 issue of
"Astounding":

    "[Clarke is commenting on an article in which] Whitton remarks, re the
    lunar dust layer, 'Our experimental limitations keep us, of course,
    from probing farther beneath.'  Actually, Australian radio physicists,
    working on 24,000 Mc/s, have already got about a meter inside the Moon!
    They have shown that the dust layer is probably only about 1mm thick,
    with solid rock underneath.  For full details, see 'Microwave Thermal
    Radiation From the Moon,' J. H. Piddington and H. C. Minnett (Aus. J.
    Sci.  Res. 2, 63-77 -- March 1949)."

(Now, obviously "Astounding" is not the journal of choice in these matters,
but while ACC may not be a true expert on these things, he is usually quite
well-informed and does cite what appears to be a credible source.)

So my question --preferably to someone who was on the scene: Was this (the
possible sinking in lunar dust) a real concern?  If it wasn't, is this just
another NASA- related urban legend?  If it was, why was there still concern
~two decades after the issue was apparently resolved?

N

P.S. BTW, I hope it's clear this not meant in any way as a flame; just
trying to resolve an apparent contradiction.  -- N

Note follow-ups.

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

Date:         Fri, 19 Oct 90 15:32:09 CDT
From: David Smith <[e-mail]>
Subject:      Re: SPACE Digest V12 #464

please unsub. me from this list, it is very interesting, but I no longer
have the time to read these, thank you for this list and the info though.

David Smith
TCDS000 at TCSVM or at VM.TCS.Tulane.Edu

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

Date: 19 Oct 90 23:44:34 GMT
From: sdd.hp.com!uakari.primate.wisc.edu!abcfd20.larc.nasa.gov!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Ulysses Update #2 - 10/19/90


                          Ulysses Mission Status
                            October 19, 1990

     The Ulysses spacecraft is now 7,172,766 miles (11,543,435 km) from
Earth and 498,753,202 miles (802,665,473 km) from Jupiter.  It is traveling
91,503 mph (147,261 kph) relative to the Sun, and 24,752 mph (39,834 kph)
relative to the Earth.

     The first TCM (Trajectory Correction Maneuver) was successfully
completed on the October 18.  Detailed evaluation of the resulting change
in trajectory has commenced. The spin rate was adjusted to 5 rpm after
the completion of TCM-1.

     The purpose of the radial manuever of TCM-1 was to correct the
direction of track of the initial trajectory.  Radial thrusters on the
spacecraft were activated in pulsed mode for a period of twenty three
hours.  Intermediate spin rate corrections were made to maintain the
spin rate of the spacecraft within pre-determined limits around 5 rpm.

     The cross coupling effects which cause a change to the spin rate
during the radial thrusters firing was less than predicted and this
therefore led to a reduction in the overall duration of the radial burn.

     The purpose of axial maneuver of TCM-1 was to increase the velocity of
the spacecraft along the direction of track.  Axial thrusters were
activated for a total of about one hour, the burns being split into two
separate manuevers. The first longer manuever was interrupted on-board
forty seconds after commencement due to a higher than expected spin rate
change caused on-board protection logic criteria to be exceeded. The AOCS
(Attitude and Orbit Control Subsystem) was configured for on-board spin rate
control during the manuever and was re-started. The manuever was completed
without incident.

     KEP (Energetic Particle and Interstellar Neutral Gas) experiment
switch-on and GAS (Neutral Gas experiment) cover release commands were
uplinked  to the spacecraft as time-tagged commands for execution
on October 19.

     The initial switch-on will be almost immediately followed by the
release of all protective experiment covers (with the exception of the LAN
experiment). The LAN experiment measures low energy charged particles. The LAN
cover will not be released until the TCM-2 has been completed.

     Thermal reconfigurations have been carried out to maintain the desired
thermal environment.  A special thermal reconfiguration was utilized during the
first TCM to maintain the thruster block temperatures within limits.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 20 Oct 90 17:53:10 GMT
From: bu.edu![e-mail]  (Steve Lehar)
Subject: Re: Theories needed on life

[e-mail] (Joe Dellinger) states:

Joe |
Joe | All the  animals we  normally   think of, things   like lizards,
Joe | bears, dogs,  whales, horses,  people,  monkeys, snakes etc, are
Joe | variations  on a remarkably  consistent  theme.  A backbone with
Joe | vertebrae, 4 limbs, five digits  per limb,  one head, one  tail,
Joe | etc etc.
Joe |   .
Joe |   .
Joe |   .
Joe | It's just far faster for evolution to keep ringing variations on
Joe | the old themes as needed than it is to invent something new from
Joe | scratch.  New inventions don't stand  a chance competing against
Joe | the old established monopolies.
Joe |

Recent studies in reaction-diffusion  theory  reveal some  interesting
phenomena in morphogenesis.  It seems  that morphogenic substances  in
the early  embryo (at the blastula  stage, where there  is essentially
just  a lump  of uniform  cells)  participate  in  resonating chemical
feedback reactions- with two  morphogens  catalysing  the formation or
destruction of themselves or each other.  The result is stable spatial
patterns of chemical concentrations,  that 'resonate' in the  'cavity'
(body mass) of  the embryo  creating patterns very like  the vibration
patterns of a drum  or tuning fork.  This  mechanism is very different
from passive diffusion of a  morphogen through  a tissue, because  the
patterns depend very   much on  the  shape  and volume of  the tissue.
(Welsh et al. [1] illustrates this phenomenon with spatial patterns of
concentration in a test tube of originally uniform composition)

Consider the case  of the hydra- you cut  it in  half, and the  bottom
half  develops  tentacles at  the   severed end,  while  the  top half
develops  a  foot.   This occurs  regardless  of where  you bisect the
creature.     Passive  diffusion of  morphogens cannot   explain  such
phenomena, but the reaction diffusion model can.

Where this bears on  the argument about  the  shapes of life  forms is
that there  are certain types of patterns   that  morphogens can form.
For instance,  James Murray  [2]  shows that spots,  stripes and other
markings  on animals  always follow certain  patterns- since  they are
produced by the same diffusion reaction  mechanism-  the difference in
the patterns being a result of the geometry of the embryo at  the time
that  the pigmented cells are  determined.  For instance, all  spotted
animals get  rings at  the  tapered tips of their  tails-  and  yet no
striped animal ever has spots on their tail.

Similar morphogenic reactions in effect  in the early embryo determine
the  fundamental morphology of the  creature.  In particular, repeated
segmentation of the body plan is as natural as rings on a tail.   This
explains  why such diverse  creatures as   humans and  insects have  a
fundamentally segmented architecture.

Here is another interesting model put forward  by Newman &  Frisch [3]
to  explain the  differentiation  of  the limb bud   tissue in a chick
embryo into muscle and  bone  progenitors.   It seems that  a reaction
diffusion resonance takes place in the tip of the  limb bud, where the
resonant patterns change  as the limb bud  grows.  The initial pattern
has a one striped  resonance,  which then becomes   a two striped  and
finally a three striped pattern as the resonant 'cavity' expands.  All
this time, the tip of the limb bud is growing outwards,  so it 'leaves
behind' first  a single,  then a double and finally  a triple trail of
bone progenitor.

     STAGE 1          STAGE 2           STAGE 3

    ff        ffff        ffffff
    BB        ffBB        ffffBB
    ff        BBff        ffBBff
            ffBB        BBffBB
<-proximal        ffff        ffBBff
  distal->                ffffBB
               ^        ffffff
  f = flesh           |             ^
  B = bone           |             |
               |             |
        Growth AND chemical resonance only occurs in the tip of
        the limb bud- i.e. the right hand column in this figure.
        The tip grows left to right, leaving behind a limb, and
        the limb expands in size the whole time.

This  explains why  the chick has  three toes,  two  distal  leg bones
(radius and   ulna) and   one  proximal  leg   bone (femur).   What is
significant about this model is that it  suggests  that the pattern of
fewer  bones  proximally to many  bones    distally  is a  fundamental
property of diffusion reaction in a growing limb  bud,  and might well
appear in alien life forms as well.

This is not to refute Joe Dellinger's statement that it is  easier for
nature to adapt  an old  life form to  a new environment than to start
from scratch, but simply to say that a lot of the apparantly arbitrary
choices made by nature along the way (such as why  we have a segmented
body  plan, or  why we have one bone  in the upper leg and  two in the
lower leg) may not have been as arbitrary as they first seemed.

[1] Welsh, B.,  Gomatam,  J., &  Burgess, A. (1983) Three  Dimensional
Chemical Waves in the Belousov-Zhabotinskii Reaction.  NATURE Vol. 304
611-614

[2] Murray,  J.  (1988) How  The  Leopard Gets Its  Spots.  SCIENTIFIC
AMERICAN, March 1988 Volume 258 Number 3

[3]  Newman   S.  & Frisch  H.  (1979)  Dynamics of  Skeletal  Pattern
Formation in Developing Chick Limb.  SCIENCE VOL 205, 662-668
--
(O)((O))(((O)))((((O))))(((((O)))))(((((O)))))((((O))))(((O)))((O))(O)
(O)((O))(((               [e-mail]               )))((O))(O)
(O)((O))(((    Steve Lehar Boston University Boston MA     )))((O))(O)
(O)((O))(((    [phone] (H)   [phone] (W)     )))((O))(O)
(O)((O))(((O)))((((O))))(((((O)))))(((((O)))))((((O))))(((O)))((O))(O)

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

Date: 19 Oct 90 03:49:07 GMT
From: usc!samsung!munnari.oz.au!metro!cluster!minnie![e-mail]  (Paul O'Donnell)
Subject: Re: Venus/Magellan, poles


In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>In article <901017.113902.EDT.JEFF@UTCVM> [e-mail] (Jeffrey R Kell) writes:
>>spin, etc., but to ask a possibly silly question,  HOW do you determine
>>where a longitude grid BEGINS?  Find Greenwich, Venus? ( ;-) )
>Ariadna Crater is used as the prime meridian on Venus.  It is a small

Yes, but is there a general rule for this or does someone need to
specify a geographical point for each planet?

Paul O'Donnell
[e-mail]
.signature: No such file or directory

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End of SPACE Digest V12 #476
*******************