Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v09_4/v9_465.txt

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Subject: SPACE Digest V9 #465

SPACE Digest                                      Volume 9 : Issue 465

Today's Topics:
             Re: Magellan update
            "it's been light years . . ."
      Re: SPACE Digest V9 #453 - Asteroids and Dinosaurs
              Re: Space telescope delays
             Re: Private Space Companies
           Magellan Status of 05/26/89 (Forwarded)
             Re: Private Space Companies
        Oort cloud (was: Re: The late NEMESIS Theory)
            Re: asteroid almost hits earth
                 Neptune pix
        Re: Meteorite impact in Soviet Union in 1947.
----------------------------------------------------------------------

Date: 26 May 89 02:29:13 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Magellan update

In article <[e-mail]> [e-mail] (Peter Scott) writes:
 [several K of mindless drivel via DASnet ]

I dunno about other folks but I am *SO GLAD* we are bridging to other nets!!!
:-)
--
Tom Neff                UUCP:     ...!uunet!bfmny0!tneff
    "Truisms aren't everything."    Internet: [e-mail]

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

Date: 25 May 89 18:40:03 GMT
From: thorin!lhotse![e-mail]  (James Symon)
Subject: "it's been light years . . ."

In article <[e-mail]>, [e-mail] (Neal Woodall) writes:
> In article <[e-mail]> [e-mail] (Tom Neff) writes:
>
> >>I am never so frustrated and morose about our prospects for the future as
> >>when I find someone misunderstanding science.  Phrases like "it's been
> >>light-years since I saw home" (_Hard Time on Planet Earth_) ...
> . . .
> It seems to me that the original poster made a misinterpretation of the
> phrase he posted....I don't really see what is "wrong" about describing
> a journey in terms of distance rather than time, or vice-versa.
>

I see. They meant it the way some story's trucker-hero would say,
"It's been five hundred miles since I saw home." Come on. You're being
overly generous, especially since this is a common mistake, and we're
talking about a throw away line in a typically dimwitted TV show
designed for the masses! Besides, even if the writers WERE waxing
poetic, my cynicism convinces me the usage was lost on 97% of the
audience and it just reinforced their misconception.

Reminds me of A&W Root Beer's ad campaign that said, "Wet your
appetite!" Aargh! Even if I could believe the writer intended the
mistake as cute irony, it was still a disservice.

jim
[e-mail]
{decvax uunet}!mcnc!unc!symon

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

Sender: "John_A_Kostecki.WBST207V"@Xerox.COM
Date: 25 May 89 05:31:43 PDT (Thursday)
Subject: Re: SPACE Digest V9 #453 - Asteroids and Dinosaurs
From: "John_A_Kostecki.WBST207V"@Xerox.COM
Cc: "John_A_Kostecki.WBST207V"@Xerox.COM
Reply-To: "John_A_Kostecki.WBST207V"@Xerox.COM

In article <agate!web-2c.berkeley.edu![e-mail]  (The
Daimyo) writes:
>The extinctions of the dinosaurs was one and about 300 million years
later,
>the extinction of pre-historic mammals another.  Before then, the
>geological record shows extinction after extinction at roughly 300 million
>year intervals.

It's been a while since I've been actively involved in the geology "game"
so I'm not 100% familiar with all the literature.  There are some problems
with the numbers you mentioned.  I accept that you were doing it from
memory, so I don't want to act picky.  Anyway, about those extinctions:
    1) the final dinosaur extinctions occured about 110 - 90 million years
ago. This is coincidental with what we call the Cretaceous/Tertiary Event.
The event was marked not only by the passing of the last "dinosaurs", but
also marked the demise of several hundred marine plankton species.  Since
the study of marine phytoplankton (one-celled plants) was one of my areas
of concentration, I had to do some work on this stuff once.  The main
points are that dinosaurs weren't the only organisms effected by the
environment at the end of the Cretaceous, but also that this last major
extiction occured at about 90 mypb (mil yrs before present).
    2) the last major extinction prior to to Cretaceous/Tertiary was the
Permo/Triassic Event, which I think was about 450 mybp.

Prior to that, there were other minor extinctions which might have wiped
out classes of species or entire phyla, but in most cases there are still
living decendents of these species.  One theory of the mass extinctions is
that there was some other factor in the environment which caused these mass
deaths.  Something which we also need to understand is that we, ie,
mankind, has been around for only a few tens of millions of years.  When
you consider that our accurate records have only been kept back to biblical
times (a span of 5000 years at best), and the major portion of the fossil
record goes back only to the Pre-Cambrian (Archeozoic), which is 600+ mybp,
our own records and recollections and comparisons of time are somewhat
warped.  What I mean is that a "mass extinction" in the fossil record may
represent 10s of millions of years in the older strata, and maybe several
hundred thousand years in the most recent events.  How do we compare the
extinctions of present day animal species with those which occured at the
Permo/Triassic Event?

Anyway, there were some other theories posed based on less spectacular
causes.  One is that the sea-floor spreading and continental drift which
are a major part of modern theories of plate tectonics and mountain
building, may also be the cause of major climatic or at least environmental
changes.  Lets look at the events occuring in the Mesozoic (450 - 90 mybp).

During the begining of this era, the Triassic strata in the US shows
evidence on the east coast of the initial stages of the breakup of a major
continent.  As we go into the Jurassic, there is evidence of large shallow
seas in the US midcontinent.  These shallow seas would have opened millions
of square miles of continental shelf to the species living at that time and
caused the vast "flowering" of species we see in the record.  The reason
for the shallow seas is interesting.  When I participated in a cruise
sponsored by the Deep Sea Drilling Project in 1980, one of the chief
scientists had proposed that this might have been caused by the increase in
sea-floor spreading rates seen at this time, ie, with all the lava pushing
up at the mid-ocean ridges, there was an increase in ocean floor volume and
thus the oceans were "pushed" upon the plains areas of all the continents.
These shallow seas did one other thing in that they caused a more temperate
climate and added more warm waters to the seas.  As the end of the Mesozoic
(Cretaceous) started to arrive, the spreading decreased, thus the volume of
the sea-floor decreased, therefore, the shallow seas were no longer there -
now only the thin continental shelves we see today.  This caused a major
ecological disaster because of the loss of this environment, greater
competition in the food chain, and only the strong or more biologically
successful survived.

The evidence of the asteroid/meteorite might be convincing as a means of
explaining the "last gasp" of the dinosaurs, but I'm not particularly
convinced that it was the ultimate cause.  Most of the similar types of
events in the past century, such as the explosion of the island of
Krakatoa, did lead to localized killings, but did not have much of a
world-wide impact, except for lowering average temperature a little and
prolonging the twilight times of the day for several years.  If we look at
Mt. St. Helens, the forrests denuded by the explosion are now growing back.
The question which this raises is what would the size of the asteroid have
to be to cause a mass extinction, but only be selective?  Remember, mammals
survived the Event, but most of them were small, just as some dinosaurs
species, so what was it that could have caused the problem?

Well, enough for now.

John A. Kostecki
Xerox Corp.
Webster, NY

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

Sender: "Dennis_C._Brantly.WBST129"@Xerox.COM
Date: 25 May 89 04:46:56 PDT (Thursday)
Subject: Re: Space telescope delays
From: [e-mail]
Cc: [e-mail]


For those interested in the process by which time is to be allocated for
observational use of the Space Telescope, and/or how the Space Telescope is
to operate (blockage of large areas of viewing by the earth/sun, warm-up of
selected instruments, locking on a designated viewing area, etc.), I would
recommend an article in the June 89 issue of Astronomy magazine:

"From Idea to Observation: The Space Telescope at Work"; an astronomer's
request for observing time on the Hubble Space Telescope sets off a complex
sequence of scheduling, observing, and data analysis, by Ray Villard.

Dennis...
Brantly:WBST129:Xerox
Webster, NY

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

Date: 26 May 89 12:52:29 GMT
From: prism![e-mail]  (Matthew DeLuca)
Subject: Re: Private Space Companies

In article <[e-mail]> [e-mail] (T.S. Reddy) writes:
>>
>     I doubt that Boeing can develop a new space vehicle given that it
>cannot even build a new airliner from scratch without collaborating with
>another company or without government aid.

     Er, what planes, what company, and what government?  I don't know about
all of their planes, but I don't recall the government subsidizing the
development of the 757 and 767, and I don't know what you mean by
collaboration; Boeing is 'borrowing' workers from Lockheed, here in Atlanta,
and they do contract some of their work out ,butI don't think that qualifies
as collaboration.  I have to agree with Henry (I think it was Henry...);
Boeing is probably the only company that can develop it's own launch system.

--
--------------------------------------------------------------------------------Matthew DeLuca                      :
Georgia Institute of Technology     :          [This space for rent]
ARPA: [e-mail]      :
--------------------------------------------------------------------------------

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

Date: 26 May 89 22:27:03 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Magellan Status of 05/26/89 (Forwarded)


                         MAGELLAN STATUS
                          May 26, 1989


     After today, the Magellan status reports will be available
only once a week, unless warranted by spacecraft activity.

     The twice daily momentum wheel desaturations and the daily
star calibration were performed routinely Thursday.

     Analysis of last Sunday's trajectory correction maneuver
indicates an achieved velocity of 2.967 meters per second,
versus a desired 2.935 meters per second. The execution error was
less than 1.1 percent.

     The final spacecraft parameters for Cruise-3, the next
spacecraft computer command sequence, have been given to the
spacecraft team's Upload Preparation Group. Cruise-3 will be
uploaded next Tuesday afternoon, May 30.






     SPACECRAFT
     Distance From Earth (mi)                   3,192,936

     Velocity  Geocentric                         5,674 mph
               Heliocentric                      60,213 mph

     One Way Light Time                           17.5 sec

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

Date: 26 May 89 15:51:41 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Private Space Companies

In article <[e-mail]> [e-mail] (T.S. Reddy) writes:
>     I doubt that Boeing can develop a new space vehicle given that it
>cannot even build a new airliner from scratch without collaborating with
>another company or without government aid.

I'm not aware that it's ever had government aid for airliner development.
(Once or twice it has developed airliners that were related to, or
descended from, government projects.  Contrary to popular misconception,
the KC-135 and the 707 are **not** the same aircraft -- they don't even
have the same fuselage cross-section -- although they share a common
[privately funded] ancestor.)  As for collaboration with other companies,
certainly Boeing prefers to spread the investment and risk around as much
as it can -- who wouldn't? -- but there is no question that Boeing has
the resources to go it alone if necessary.

Boeing's current commercial order backlog is over 1500 airliners.  That's
over 75 BILLION dollars.  And you can bet they're making a profit on it.
--
Van Allen, adj: pertaining to  |     Henry Spencer at U of Toronto Zoology
deadly hazards to spaceflight. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 26 May 89 23:40:48 GMT
From: usc!csun!solaria![e-mail]  (Stephen Walton)
Subject: Oort cloud (was: Re: The late NEMESIS Theory)

In article <[e-mail]>, nather@ut-emx (Ed Nather) writes, in
response to Bill Wyatt ([e-mail]):

>Apparently you know of observational evidence that I don't -- would you
>please cite it, bearing in mind that the theory was devised to explain the
>origin of comets, so their presence is not evidence the theory is correct?

I was going to summarize a bunch of arguments here, but just re-read
the section of the text I used this year for intro astro (Abell,
Morrison, and Wolff, _Realm of the Universe_, 4th edition). An excerpt:

"Observationally, the aphelia of new comets typically have values near
50,000 AU.  This clustering of aphelion distances was first noted by
Dutch astronomer Jan Oort, who proposed in 1950 a scheme for the
origin of the comets that is still accepted today."

This passage was written by the second author, David Morrison, a very
well informed planetary astronomer of my acquaintance (I'm a solar
physicist, and thus not really qualified to pass judgement).  However,
Morrison goes on to write:

"Just because most new comets have _aphelia_ near 50,000 AU, we should
be careful not to conclude that the Oort cloud consists of billions of
comets in roughly circular orbits at this distance, like a shell
around the Sun.  There may be some comets in nearly circular orbits,
but if so, we have no evidence of them."

He then notes that a passing star can cause only small perturbations
in an orbit, so that a new comet with perihelion 1 AU cannot have had
a perhelion of more than a few AU on its previous orbit.  On the other
hand, this means that there must be many, many comets in the outer
solar system for every one which we observe;  Object Chiron is a
possible example, though a large one:  occultation measures give its
diameter as at least 100 km.

So, both Bill and Ed are partly right, I guess.  There is no evidence
for the spherical shell which is the picture most of us have of the
Oort cloud, but there are still many more comets in the outer solar
system.
--
Stephen Walton, Dept. of Physics & Astronomy, Cal State Univ. Northridge
[e-mail]       [e-mail]
[e-mail]    ...!csun!afws.csun.edu!ecphssrw

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

Date: Fri, 26 May 89 10:41:49 PDT
From: Peter Scott <[e-mail]>
Subject: Re: asteroid almost hits earth

agate!shelby!Portia!hanauma![e-mail]  (Joe Dellinger) writes:

>    Incidentally, some geophysicists are waiting quite impatiently
>for another mag 9 mega-quake.

This is a great source of comfort to all of us in Southern California...

Peter Scott ([e-mail])

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

Date: Fri, 26 May 89 12:07:31 PST
From: Peter Scott <[e-mail]>
Subject: Neptune pix
X-Vms-Mail-To: EXOS%"[e-mail]"

The latest issue of the JPL _Universe_ (in-house newspaper) has a couple of
pictures of Neptune, showing about the detail you get of Mars from a small
amateur scope (say, 6").  Unfortunately I can't reproduce them here, but the
caption is interesting nevertheless:

NEARING NEPTUNE -- These Neptune images by Voyager 2 on April 26 were from 176
million kilometers (109 million miles).  The picture at right was taken five
hours after the left, during which time the planet rotated 100 degrees.  The
dark spot visible in the left photo was in images obtained three months earlier
[said dark spot is about the size and latitude of North Africa if the disk were
Earth's].  A brighter white spot, prominent earlier, has apparently faded.  The
white spot near the south pole in the right picture is new [looks slightly
smaller than Greenland, by the same analogy, tho' at the other end of the
planet].  It was visible faintly in a picture 18 hours earlier at the same
longitude.

Can't wait for us to get close enough to resolve the 90-mile high statue of
Elvis which we *know* must be there :-)

Peter Scott ([e-mail])

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

Date: 26 May 89 20:34:48 GMT
From: megatest![e-mail]  (Ivan Batinic)
Subject: Re: Meteorite impact in Soviet Union in 1947.


    If memory serves me, this was known as the "Tingustu Event"
(or something close to that).  Witnessed by many from afar, there
were reports of extremely high-intensity light from the horizon.
An enormous circular section of forest was flattened and flash-
burned.  However, NO CRATER nor evidence of any crater exsists.

    Dr. C. Sagan speculated that this could be explained by the
advent of a "piece" of comet material (methane ice) impacting the
earth, causing a huge gas-explosion.

    I believe there are actual documents reporting the incident,
however I have no idea how to locate them.

    I hope I have not confused two separate events here.  It would
be amusing if "lightning" (as it were) did strike twice in one place!

    Ivan

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DISCLAIMER: Blah-blah, Woof! Woof!

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

End of SPACE Digest V9 #465
*******************