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Date: Mon,  8 Mar 93 05:10:54
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Space Digest                Mon,  8 Mar 93       Volume 16 : Issue 289

Today's Topics:
     Electronic Journal of the ASA (EJASA) - March 1993 [Part 1]

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Date: Sun, 7 Mar 1993 23:05:20 GMT
From: Larry Klaes <[e-mail]>
Subject: Electronic Journal of the ASA (EJASA) - March 1993 [Part 1]
Newsgroups: sci.astro,sci.space,sci.misc,sci.geo.geology,alt.sci.planetary

                          THE ELECTRONIC JOURNAL OF
                  THE ASTRONOMICAL SOCIETY OF THE ATLANTIC

                       Volume 4, Number 8 - March 1993

                         ###########################

                              TABLE OF CONTENTS

                         ###########################

          * ASA Membership and Article Submission Information

          * The Soviets and Venus, Part 2 - Larry Klaes

                         ###########################

                         ASA MEMBERSHIP INFORMATION

        The Electronic Journal of the Astronomical Society of the Atlantic
    (EJASA) is published monthly by the Astronomical Society of the
    Atlantic, Incorporated.  The ASA is a non-profit organization dedicated
    to the advancement of amateur and professional astronomy and space
    exploration, as well as the social and educational needs of its members.

        ASA membership application is open to all with an interest in
    astronomy and space exploration.  Members receive the Journal of the
    ASA (hardcopy sent through United States Mail - Not a duplicate of this
    Electronic Journal) and the Astronomical League's REFLECTOR magazine.
    Members may also purchase discount subscriptions to ASTRONOMY and
    SKY & TELESCOPE magazines.

        For information on membership, you may contact the Society at any
    of the following addresses:

        Astronomical Society of the Atlantic (ASA)
        c/o Center for High Angular Resolution Astronomy (CHARA)
        Georgia State University (GSU)
        Atlanta, Georgia  30303
        U.S.A.

        [e-mail]

        ASA BBS: [phone], 300/1200/2400 Baud

        or telephone the Society Recording at [phone] to leave your
    address and/or receive the latest Society news.

        ASA Officers and Council -

        President - Eric Greene
        Vice President - Jeff Elledge
        Secretary - Ingrid Siegert-Tanghe
        Treasurer - Mike Burkhead
        Directors - Becky Long, Tano Scigliano, Bob Vickers
        Council - Bill Bagnuolo, Michele Bagnuolo, Don Barry, Bill Black,
                  Mike Burkhead, Jeff Elledge, Frank Guyton, Larry Klaes,
                  Ken Poshedly, Jim Rouse, Tano Scigliano, John Stauter,
                  Wess Stuckey, Harry Taylor, Gary Thompson, Cindy Weaver,
                  Bob Vickers


                             ARTICLE SUBMISSIONS

        Article submissions to the EJASA on astronomy and space exploration
    are most welcome.  Please send your on-line articles in ASCII format to
    Larry Klaes, EJASA Editor, at the following net addresses or the above
    Society addresses:

        [e-mail]
        or - ...!decwrl!verga.enet.dec.com!klaes
        or - [e-mail]
        or - [e-mail]

        You may also use the above addresses for EJASA back issue requests,
    letters to the editor, and ASA membership information.

        When sending your article submissions, please be certain to include
    either a network or regular mail address where you can be reached, a
    telephone number, and a brief biographical sketch.

        Back issues of the EJASA are also available from the ASA anonymous
    FTP site at chara.gsu.edu (131.96.5.29).  Directory: /pub/ejasa

                                DISCLAIMER

        Submissions are welcome for consideration.  Articles submitted,
    unless otherwise stated, become the property of the Astronomical
    Society of the Atlantic, Incorporated.  Though the articles will not
    be used for profit, they are subject to editing, abridgment, and other
    changes.  Copying or reprinting of the EJASA, in part or in whole, is
    encouraged, provided clear attribution is made to the Astronomical
    Society of the Atlantic, the Electronic Journal, and the author(s).
    Opinions expressed in the EJASA are those of the authors' and not
    necessarily those of the ASA.  This Journal is Copyright (c) 1993
    by the Astronomical Society of the Atlantic, Incorporated.


                             THE SOVIETS AND VENUS
                                     PART 2

                       Copyright (c) 1993 by Larry Klaes

    The author gives permission to any group or individual wishing
    to distribute this article, so long as proper credit is given,
        the author is notified, and the article is reproduced in its
        entirety.

        The Last of the First Generation

        With the surface of the planet Venus finally attained through the
    success of VENERA 7 in late 1970, the Soviet Union decided to send one
    more set of their first-generation Venus probes to the shrouded world
    to improve upon the limited data already gathered by VENERA 7.  This
    was required for planning the more sophisticated VENERAs which would
    follow in the coming years.

        On March 27 and 31, 1972, two spacecraft were lofted from the
    Kazakhstan Republic into Earth orbit during the one good Venus launch
    window of that year.  The first vehicle, VENERA 8, was boosted away
    from its parking orbit into deep space.  The second VENERA did not
    escape Earth's gravity and was quickly designated COSMOS 482, where
    it remained in a highly elliptical path until May of 1981.  This was
    the last known major failure of a Soviet Venus probe to date.

        The primary task of VENERA 8 was to deposit the first lander on
    the day side of Venus (COSMOS 482 had been meant to drop its lander
    on the planet's night side).  The information returned by earlier
    Venus vessels allowed VENERA 8's designers to modify the spacecraft
    series once again.  This time the lander was given precisely tailored
    environmental protection to make space for more scientific devices.
    A second omni-directional antenna was added to VENERA 8.  This way,
    if the lander tipped over like VENERA 7 had, it could still clearly
    broadcast its measurements back to Earth.

        On July 22, the small metal VENERA robot flew into the planet
    Venus, detaching the sealed instrument package into the yellowish
    clouds before the rest of itself was burned up by atmospheric fric-
    tion.  The capsule made a rapid descent to the far eastern region
    of Navka Planitia, 2,896 kilometers (1,738 miles) from VENERA 7's
    touchdown site.  Once on the surface, VENERA 8 ejected its extra,
    disc-shaped antenna onto the ground several meters away and began
    reporting about the immediate external conditions.  The lander
    transmitted from Venus for fifty minutes before succumbing to the
    rising internal heat.

        The VENERA 8 lander was loaded with a wide variety of instruments
    for making numerous measurements not attempted with its predecessors.
    During its descent through Venus' atmosphere, the probe conducted an
    analysis for ammonia, finding no more than 0.1 percent of the gas
    present.  VENERA 8 clocked the horizontal velocities of the winds
    buffeting it at various altitudes.  Venus' wind speeds ranged from
    a strong one hundred meters (330 feet) per second over forty-eight
    kilometers (twenty-nine miles) from the surface to just one meter
    (forty inches) per second below ten kilometers (six miles).  The
    winds moved in the same direction as the planet's rotation, though
    much faster.

        On the planet, VENERA 8 refined the surface temperature and
    pressure readings made by VENERA 7.  Now the ground temperature was
    placed at 470 degrees Celsius (878 degrees Fahrenheit), plus or minus
    eight degrees.  The crushing air pressure was verified at ninety bars,
    this time with an accuracy variance of only 1.5 bars.

        The density of the Venerean soil was given an examination using
    the second omni-directional antenna, while its composition was studied
    with a gamma-ray spectrometer.  Initially, the surface at the unmanned
    craft's landing site was thought to be an upland plain made of loose
    granite, possibly a very ancient part of Venus' crust.  More recent
    studies indicate that the soil around VENERA 8 is probably a rare form
    of basalt, one with high potassium levels.  Did basaltic lava from
    erupting volcanoes once flow across Navka Planitia?

        Light levels from the Sun were also measured at this location
    using instruments called cadmium sulfide photoresistors.  These
    devices relayed data which seemed to indicate that few solar photons
    penetrated the obscuring cloud decks to the surface.  Apparently, even
    in Venus' long daytime, the sky was no brighter than twilight on
    Earth.  An observer would be able to see objects no more than one
    kilometer (0.62 mile) away in the darkness, if that.  Later on it
    would be learned that the lander came to rest when the Sun was just
    five degrees above the local horizon.  High noon on Venus was much
    brighter than thought at the time.

        Advanced as VENERA 8 was over the Soviet craft that explored
    Venus before it, the probe had merely hinted at the surprises in store
    for the new machines to follow.  The first generation probes had shown
    scientists what the planet was like in and under its clouds.  The next
    generation would begin to reveal the long history of how Venus had
    come into its present state.

        On the Way to Mercury

        The year 1973 marked an unusual event for the Soviet space program:
    For the first time since the VENERA missions of 1961, no space vehicles
    of Soviet manufacture were sent to Venus during a favorable launch
    window.  Soviet spacecraft designers were busy constructing the second
    generation of their prestigious VENERA probes, which would not be ready
    until the Venus launch window in middle 1975.

        The people in charge of the Venus program apparently felt that
    enough information had been gathered about the perpetually cloudy
    planet by their first generation probes and the American missions to
    make a further expedition with the same type of spacecraft merely
    redundant.  In addition, the Soviets had their hands full in 1973
    with a second LUNOKHOD roaming the dusty surface of Earth's moon, the
    monitoring of four new unmanned craft heading to Mars, and the slow
    reactivation of their SALYUT space station program after the tragic
    loss of the SOYUZ 11 crew in June of 1971.

        The United States had their own intentions for Venus during this
    intervening period, though the shrouded world was not NASA's primary
    goal for their latest planetary mission.  Venus was to serve as an
    important gravity assist for the MARINER 10 spacecraft, which was
    aimed for the smallest of the terrestrial worlds, Mercury.

        Until the early 1970s, Mercury was a place as nearly mysterious
    as Venus.  Due to its relative distance from Earth and close proximity
    to the glaring Sun, features on this ancient world were seen faintly
    at best.  It was up to MARINER 10 to flyby Mercury and reveal its true
    face to humanity.

        Launched from Cape Canaveral on November 3, 1973 aboard an ATLAS-
    CENTAUR rocket, MARINER 10 was destined to make the first two-planet
    flyby mission in space history.  Despite a number of threatening tech-
    nical problems which arose shortly after launch, MARINER finally came
    under the gravitational influence of Venus in early February of 1974.
    The probe's flight path had to be precise, or Venus' mass would deflect
    the vehicle away from Mercury.

        On February 5, MARINER 10 skimmed just 5,768 kilometers (3,461
    miles) above Venus' hidden surface.  The probe's various cameras
    imaged the planet for the first time from nearby space, showing
    scientists that photographing Venus above its cloud deck could give
    more useful information about the planet than previously thought.
    Measurements of the clouds taken in ultraviolet light verified earlier
    indications that the planet's upper atmosphere sped around Venus in
    just four Earth days, far faster than its rotation period of 243.1
    Earth days.  Intricate details in the thick clouds only glimpsed at
    through Earth telescopes in the past were brought into full focus by
    the craft.

        Other instruments aboard MARINER 10 reported that Venus' temper-
    atures from the top of its atmosphere to the surface varied little
    across the planet.  MARINER gave further evidence for the lack of a
    planetary magnetic field, in part by the strong influences of the
    solar wind on the Venerean ionosphere.  Unable to remain, the third
    successful American spacecraft to Venus - and the first since MARINER
    5 seven years ago - sailed on to its historic encounter with Mercury
    in late March.

        The Face of Hell Revealed

        Exploration of Venus by Soviet spacecraft got back into full swing
    by the launch window of 1975.  As predicted, the more advanced second
    generation of VENERA vehicles were to be the latest emissaries from
    Earth.  In basics, these new machines were similar in design to their
    Soviet predecessors, consisting of a main bus with large solar panels
    on either side and an attached lander (inside a protective aeroshell)
    for making surface studies.  Here, though, the resemblances abruptly
    ended.

        The two vessels, to become known as VENERA 9 and 10, carried far
    more instrumentation than any such spacecraft before.  The result
    of these improvements were to make the new VENERAs the biggest and
    heaviest Venus probes yet built.  The complete VENERA 9 craft measured
    6.7 meters (22.11 feet) across with the solar panels extended.  The
    probe weighed a total of 4,936 kilograms (10,859 pounds), with 660
    kilograms (1,452 pounds) of that being the improved lander.  VENERA 10
    weighed 97 kilograms (213 pounds) more overall.  The increased mass
    forced the Soviets to switch from using the old MOLNIYA rockets to the
    more modern and powerful PROTON boosters, which had already proven
    themselves as heavy lift vehicles on Luna and Mars missions.

        The main buses of the two VENERAs would neither fly by the planet
    nor plunge into the turgid atmosphere to their destruction.  Instead,
    they would become the first space vehicles to circle the second world.
    The orbiters were equipped to image the planet's cloud cover, along
    with measuring its brightness, reflectivity, and temperature.  Other
    devices were carried to search for any evidence of even a minute
    planetary magnetic field.  The VENERA buses also had the task of
    sending data from the deployed landers back to Earth.

        The landers underwent a series of major technical changes which
    gave the Venus explorers the unusual appearance of a sphere with a top
    hat and a wide ring (torus) surrounding the base of the ball.

        The "top hat" served a multitude of purposes:  The vertical spiral
    cylinder was the main antenna and parachute housing.  The disc under-
    neath the cylinder and overhanging the sphere was used both as a
    reflector of radio waves to the antenna and as an air brake for the
    landers during the last stages of their descent through the Venerean
    sky.  Past VENERA missions had proven that Venus' atmosphere was so
    thick that an oblate object could sink slowly enough to the planet's
    roasting surface without the aid of parachutes and survive the impact.
    This method also allowed the lander to reach the surface fast enough
    so as not to overheat while still high in the atmosphere.

        The metallic sphere housed the majority of the probes' scientific
    instruments, including an extendible radiation densitometer to measure
    the soil density and a television imaging system to give humanity its
    first optical views of Venus' elusive surface.  Just below the cameras
    were floodlights to illuminate what Soviet scientists thought would be
    a very dim landscape, due to the information from VENERA 8 three years
    prior.  The torus at the bottom would cushion the physical shock of
    the craft at the moment of touchdown and keep the lander upright.

        VENERA 9 and 10 were launched into space on June 8 and 14, 1975,
    respectively.  Four months later and two mid-course corrections apiece,
    the robot vehicles arrived in Venerean space.  On October 20, VENERA 9
    split into two components:  The main bus fired its braking engines to
    achieve a wide orbit around Venus, while the capsule was targeted for
    a planetary landing.

        On October 22, the VENERA 9 lander entered the atmosphere of
    Venus.  The descent pattern for the probe varied some from the landers
    before it.  Once air resistance had slowed down the craft, the top
    half of the lander's spherical covering was pulled away at an altitude
    of sixty-four kilometers (thirty-eight miles) by two small parachutes.
    A braking parachute then emerged to further reduce VENERA 9's velocity.

        Soon after this procedure, three main parachutes were sent
    billowing above the lander, while the lower section of the aeroshell
    was released from the probe, completely exposing the lander to the
    surrounding air.  This profile lasted for twenty minutes.  Fifty
    kilometers (thirty miles) above the planet's surface, VENERA 9 broke
    through the dense cloud cover and removed its main parachutes.  The
    lander now had to rely on its aerobrake disc to survive impending
    contact with the swiftly approaching ground.

        At 5:13 Greenwich Mean Time (GMT), the strange-looking craft
    touched down at the base of a hill in northeastern Beta Regio at a
    speed of seven meters (twenty-three feet) per second, kicking up a
    small cloud of dust upon landing.  Initial temperature and pressure
    readings in the immediate area reached 460 degrees Celsius (860
    degrees Fahrenheit) and ninety Earth atmospheres.  Winds at the
    landing site blew around VENERA up to 2.5 kilometers (1.5 miles) per
    hour.  While a similar breeze on Earth would be quite mild, Venus'
    denser atmosphere amplified the force of the wind several times.

        Fifteen minutes into its surface mission, VENERA 9's television
    cameras were automatically uncovered and activated, where they began a
    scan of the landing site in a forty by 180-degree field of view.  The
    curved black, white, and gray image eventually transmitted to Earth
    was the first of its kind ever to be returned by a spacecraft on ano-
    ther planet.  It was also a very surprising picture to the scientists
    who had assumed that the Venerean crust would be little more than a
    desert of nearly unbroken sand engulfed in darkness.

        VENERA's new home was as brightly lit as an overcast day on Earth
    (the Sun shone fifty-four degrees above the local horizon during the
    lander's fifty-three minutes of transmission time), rendering the
    floodlights unnecessary.  The ground was certainly not a bland sea of
    sand.  Both sharp and round-edged rocks embedded in soil surrounded
    the craft off into the distance, indicating that this region may have
    seen relatively recent crustal activity.  This was yet another surprise
    to scientists who thought that Venus had been geologically extinct for
    ages.  The lander also captured part of its shock-absorbing torus and
    the extended densitometer in lower portion of the historic image.

        The findings from the probe's gamma-ray spectrometer produced yet
    another new piece of information to the data sent back by VENERA 8 in
    1972.  This particular area appeared to be composed of a more common
    basaltic material than that found at VENERA 8's landing zone in Navka
    Planitia.  Later Venus missions have shown that Beta Regio consists
    of two shield volcanoes, possibly still active.

        On October 25, VENERA 10 followed a programmed route similar to
    that of its twin vessel.  The main bus inserted itself into a two-day
    orbit around Venus while the lander fell onto the planet 2,200 kilo-
    meters (1,320 miles) from the now-silent VENERA 9, in the southeastern
    corner of Beta Regio.  The craft found its examination site to be five
    degrees warmer and two bars of air pressure higher than its counter-
    part's landing area.  The winds moved at 1.3 meters (4.3 feet) per
    second.

        VENERA 10 came to rest at a slight angle on a large, flattened
    rock.  The landscape image produced by the vehicle was quite different
    from its immediate predecessor's.  The entire plain consisted of rock
    slabs and soil which appeared weathered and truly ancient, with little
    evidence of any geological activity having occurred in a very long
    time.  Despite this, composition analysis of the surface by VENERA 10
    did agree with VENERA 9, the primary soil mineral being a common type
    of basalt.

        The VENERA 10 lander transmitted twelve more minutes of information
    than did VENERA 9, though both craft may have been active even longer.
    The signals were cut by the orbiter relays when they went out of the
    landers' radio range during the surface missions.

        The orbiters themselves continued to return data through the mid-
    dle of 1976, monitoring solar wind interactions on Venus' ionosphere
    and newly discovered plasma tail.  The probes showed that liquid
    droplets existed in the atmosphere, though their actual composition
    remained to be learned.  Infrared radiation measurements on Venus'
    clouds indicated that the world's nighttime temperatures were actually
    warmer than in the day hemisphere!  Strong air streams on Venus' day-
    light half brought radiating elements to heat the dark side.  The
    orbiters also found short-period glows in the night hemisphere which
    were attributed to bursts of lightning.

        So much new information had been returned about the veiled world
    by VENERA 9 and 10 that the Soviets were forced to skip the Venus
    launch window in the winter of 1976-1977.  Extra time was required
    to modify the next group of second generation VENERA spacecraft to
    better examine the planet's latest revelations and mysteries.

        The Armada of 1978

        The late 1970s were an exciting time in planetary exploration for
    the United States.  Two space probes named VIKING had become the first
    unmanned vehicles to successfully land on Mars in 1976.  Their electric
    eyes presented an alien world of reddish deserts strewn with boulders
    under pink daytime skies.  In the summer of 1977, another team of
    vehicles named VOYAGER were launched from Cape Canaveral on a decade-
    long journey to the massive Jovian worlds inhabiting the outer solar
    system.

        By 1978, NASA had again focused its attentions on Venus, this time
    with a level of technical and quantitative sophistication unmatched by
    any U.S. Venus mission before.  The project spacecraft were designated
    PIONEER VENUS, the last in a long line of solar system explorers going
    back twenty years and spanning into the interstellar realm.

        PIONEER VENUS was divided into two space probes which appeared
    similar but had different mission goals.  PIONEER VENUS 1 (PV1, also
    known as PIONEER VENUS Orbiter and PIONEER 12) would circle the planet
    and conduct the first radar mapping of the Venerean surface from a
    location other than Earth.  PIONEER VENUS 2 (PV2, also called PIONEER
    VENUS Multiprobe and PIONEER 13) would dive straight into the planet,
    releasing four smaller craft to examine Venus' bizarre atmosphere
    from top to bottom.

        PV1 was sent from Earth on May 20, 1978, encased in the nosecone
    of an ATLAS-CENTAUR rocket.  PV2 followed on August 8.  Despite the
    separation of several months between launches, both craft were planned
    to arrive at Venus within days of each other in early December.  PV1
    required the slower flight path in order to avoid using a larger and
    more powerful orbital insertion engine, thus preventing several scien-
    tific instruments from being abandoned.  Though widely unforeseen at
    the time, PIONEER VENUS was to be the last new planetary mission for
    the United States through the end of the 1980s.

        On a less dramatic note that year, the Soviet Union launched their
    eleventh and twelfth official VENERA probes on September 9 and 14.
    Resembling the successful 1975 Venus craft, VENERA 11 and 12 cradled
    a host of new instruments for studying the second world.  Two of these
    devices were a gas chromatograph and the Groza (thunderstorm) instru-
    ment, the first designed for a more thorough analysis of the consti-
    tuents in the Venerean atmosphere and the second for detecting light-
    ning amongst the clouds.  The landers also carried improved cameras,
    meant to take the first color images of Venus' surface, and equipment
    for soil drilling and analysis.  The VENERAs would reach Venus just
    weeks after their American counterparts.

        A World of Women

        On December 4, 1978, the small cylindrical form of PIONEER VENUS
    1 fired its braking engine into a twenty-four-hour orbit around the
    giant yellow sphere of Venus.  Soon the spacecraft settled in and
    began bouncing radar beams off the planet's beguiling surface during
    each period of closest approach.  PV1's view of Venus' face was some-
    what limited in detail, since the radar could only resolve objects
    down to seventy-five kilometers (forty-five miles) in diameter.  How-
    ever, the probe was able to examine territory that remained continually
    hidden from Earth's more powerful radio telescopes, a value in itself.

        A cohesive picture of the world beneath the clouds began to emerge
    for the first time, thanks to PV1.  The overall surface of the planet
    was relatively flat:  Sixty percent of Venus' crust lay within one half
    kilometer (0.3-mile) of the mean surface.  Despite this smoothness,
    quite a few impressive geological features were found scattered across
    the globe, presenting scientists with proof of major tectonic activity
    in the planet's past.  Of particular note were two continent-size
    plateaus named Aphrodite and Ishtar Terra.  Rift valleys and possible
    volcanoes were also revealed in the radar images.

        The work of PV1 allowed for the first detailed naming of surface
    features on Venus.  The International Astronomical Union (IAU), the
    organization which gives celestial bodies their official names,
    decided that all places not already labeled by previous Earth-based
    studies be given nomenclatures of women from history and various
    mythologies.  One reason for this action was that Venus is the only
    planet in the solar system called after an ancient female deity, so
    naming its surface regions for famous women seemed only appropriate.


        PV1 went on to monitor the complex cloud structures of the planet
    and its near-space environment for well over a decade, right to its
    fiery end in the Venerean atmosphere on October 8, 1992.  The electric
    field detector found numerous indications of lightning in Venus' clouds,
    though there was considerable debate whether the readings were truly
    lightning or activity in the ionosphere.  The orbiter observed Comet
    Halley as it swung around the Sun in February of 1986, and recorded
    several gamma-ray bursts, high-energy radiation of speculative origin,
    spraying in from deep space.

        America on Venus

        In late November, PIONEER VENUS 2 was just weeks away from its
    encounter with the shrouded planet.  It was at this time that the
    main spacecraft bus began to release its cargo of four atmosphere
    craft, one Large Probe and three simpler and identical Small Probes.
    The first to be detached was the Large Probe on November 16, at a
    distance of 11.1 million kilometers (6.6 million miles) from Venus.
    The Small Probes followed suit on November 20, when the robot fleet
    was 9.3 million kilometers (5.6 million miles) from the target world.

        The Small Probes were named North, Day, and Night, corresponding
    to the areas on Venus they were programmed to impact the following
    month.  All four probes were instrument-packed spheres covered with
    conical heat shields designed to protect the craft from the heat of
    entry with the planet's atmosphere.  The Large Probe would have the
    advantage of a parachute during most of its descent through the
    Venerean air.  The Small Probes would have to depend on their heat
    shields alone to slow them in the atmosphere, much as VENERA 9 and 10
    had to rely on their aerodiscs to keep from crashing.  While none of
    the probes were meant to survive their destinies with the planet, it
    was hoped that at least a few of them would land gently enough for
    continued transmission from the ground.

        On December 9, the Large Probe became the first of PV2's compo-
    nents to plunge into Venus' dense clouds.  The probe slammed into
    the upper atmosphere at forty-two thousand kilometers (25,200 miles)
    per hour and was slowed to 727 kilometers (436 miles) per hour in just
    thirty-eight seconds.  Minutes later a small mortar on the craft was
    fired to start a chain reaction of parachute deployment and heat shield
    removal.  The Large Probe continued drifting downward, examining the
    air swishing around it.

        Almost seventeen minutes later, the parachute cords were cut from
    the seventy-three-centimeter (twenty-nine-inch) diameter sphere.  The
    probe fell free for over one half-hour to finally impact upon Navka
    Planitia at a speed of thirty-two kilometers (nineteen miles) per hour.
    The Large Probe became the first American vessel to reach the surface
    of Venus, though it did not survive the encounter.

        Minutes after their larger brother entered the Venerean atmosphere,
    the three Small Probes followed in turn, spreading out over the globe
    to sample different environments.  Falling without the support of para-
    chutes, the Small Probes surveyed their regions of air in less than one
    hour.

        First to arrive was the North Probe, coming down at night on
    Ishtar Terra just south of Maxwell Montes, the highest point on Venus.
    The craft went silent in the darkness with its thirty-five kilometers
    (twenty-one miles) per hour landing.

        The Day Probe created a cloud of dust at its landing site between
    Navka and Lavinia Planitia.  It was this loose soil which helped to
    keep the Day Probe intact and transmitting back to Earth for an im-
    pressive 67.5 minutes after touchdown.  Radio contact ended with the
    exhaustion of the probe's batteries.  Before shutting down, the craft
    reported an internal pressure buildup and temperature rise to 126
    degrees Celsius (259 degrees Fahrenheit).

        The Night Probe also kept broadcasting after its landing in Aino
    Planitia, but for only a mere two seconds.

        The last of the PV2 flotilla to reach Venus was the spacecraft bus
    itself, sailing into the planet's upper atmosphere without the benefit
    of a heat shield against air friction.  The bus returned data unobtain-
    able by its smaller companions for just over one minute before being
    destroyed roughly 120 kilometers (seventy-two miles) above Themis Regio.

        A Wild and Deadly Atmosphere

        The kamikaze jaunts of the PIONEER VENUS 2 mission confirmed earlier
    data and yielded new information on Venus' atmosphere as revolutionary
    in the study of the shrouded planet as that returned from the MARINER 2
    flyby sixteen years earlier.

        Ninety kilometers (fifty-four miles) above the surface, the probes
    began cutting through a layer of haze twenty kilometers (twelve miles)
    deep.  The next twenty-three kilometers (fourteen miles) held three
    main cloud layers, the highest of which was continually driven around
    the globe by winds moving at an incredible 360 kilometers (216 miles)
    per hour, faster than a powerful hurricane on Earth.  The bottom cloud
    deck was opaque.  Further down the air became almost stagnant and
    turned hazy again, finally clearing thirty kilometers (eighteen miles)
    from the ground.

        A number of strange events and wonderful discoveries occurred
    during the PV2 probes' one-way trip.  The temperature sensor on every
    probe shut off about sixteen kilometers (ten miles) from the surface,
    just as an intensity of infrared light was being recorded.  Other
    instruments also reacted unusually around the same time.  Electrical
    and chemical interactions with the air were blamed for the crafts'
    behavior, but actual reasons remained elusive.

        The mass spectrometer on the Large Probe, designed to identify
    atmospheric particles by measuring their various masses, was rendered
    temporarily useless when it became clogged with a cloud droplet during
    the descent.  A heater coil around the device inlet eventually boiled
    the droplet away, allowing its molecular makeup to be taken in the
    process.  The readings proved what had been theorized since 1973:
    The drop was composed of sulfuric acid, which saturated the Venerean
    atmosphere as a heavy mist.  Venus was not only extremely hot, its
    air was more corrosive than the battery acid of an automobile.

        It appeared that the acid came from the sulfur dioxide permeating
    the planet's atmosphere, which gives the Venerean clouds their yellow
    tint.  Indeed, the PIONEER VENUS Orbiter would monitor reductions in
    the amount of sulfur dioxide in the planet's atmosphere during its
    circlings of the globe.  Since sulfur dioxide is a known constituent
    of volcanic eruptions on Earth, did this mean that at least some of
    Venus' volcanoes were active and spewing out material?

        The presence of sulfuric acid and sulfur gas in the Venerean air,
    along with the known abundance of carbon dioxide, played primary roles
    in furthering support for the greenhouse theory regarding the planet's
    high temperatures.  These were the key ingredients required by the
    theory to explain how Venus kept the majority of its heat from exiting
    into space.

        The other particle found in that particular droplet provided a
    major clue to the conditions in Venus' distant past.  Deuterium, an
    isotope of hydrogen (also called heavy hydrogen), was found in quan-
    tities one hundred times greater than in Earth's oceans, where its
    highest concentrations reside on our planet.  Did this mean that Venus
    also had oceans of water ages ago?  Was Venus once more like Earth in
    its early days?  Had an atmosphere growing in carbon dioxide trapped
    the Sun's heat and increased Venus' temperatures until the oceans
    boiled away into the sky?

        The Large and Small Probes' mass spectrometers doled out one more
    tantalizing atmospheric mystery for scientists.  The inert gases neon
    and argon were found in much higher amounts than theory predicted.  It
    was assumed that Earth and the other terrestrial planets had gotten
    their air from crustal outgassing billions of years ago.  Did the data
    from Venus indicate that the planets (or at least Venus) had actually
    formed their atmospheres by collecting gases from the condensing solar
    nebula during the birth of our solar system?  PIONEER VENUS had simul-
    taneously solved and opened wide a host of riddles for future investi-
    gation, the mark of a successful expedition.

        A Mixed Bag Mission

        Two weeks after the mission end of PIONEER VENUS 2, the Soviet
    Venus exploration team made its scheduled appearance.  Since the
    VENERA craft had been sent up after the favorable Venus launch window,
    the main buses were unable to carry enough fuel to break into orbit
    about the planet.  Instead, they had to settle for heliocentric paths.
    However, this setup would allow the buses to be in longer radio contact
    with the landers than if they were circling Venus.

        Having taken a somewhat shorter flight route, VENERA 12 arrived
    on December 21.  Its twin skimmed by on Christmas Day.  Both landers
    were ejected from the passing mother craft and entered the Venerean
    atmosphere, coming down about one hour later eight hundred kilometers
    (480 miles) apart in eastern Phoebe Regio.

        The landers transmitted from the surface for record times:  Ninety-
    five minutes for VENERA 11 and 110 minutes for VENERA 12.  Impressive
    amounts of atmosphere data were released by Soviet officials.  Strangely,
    though, little was said regarding actual information on the probes'
    landing sites.

        Two of the main lander objectives had become victims of equipment
    failure.  On both craft, the color cameras' protective covers refused
    to come off.  The soil drills also failed to function as planned.
    Soviet officials decided to remain quiet on these drawbacks for the
    time being and emphasize on the probes' scientific successes.

        The reason for this loss to the study of Venus may have been due
    to secret desires for the planet Mars.  In 1989, the Soviet book RACE
    TO MARS revealed plans for an ambitious unmanned mission in the late
    1970s to bring back soil samples from the Red Planet.  The project was
    designed to upstage the plans then being considered by NASA and the
    Jet Propulsion Laboratory (JPL) for taking Martian soil of their own.
    Unfortunately, the soil sample return mission never left the ground,
    but it apparently had a profoundly negative affect on the Soviet lunar
    and Venus craft also under construction at the time.

        The Mars mission was complicated, consuming a great deal of the
    engineering resources available.  In the rush to get the vehicle into
    space, the LUNA 24 soil sample return mission of 1976 was delayed and
    a third LUNOKHOD rover eventually wound up as a museum display.  The
    camera and drill problems of VENERA 11 and 12 may have been a result
    of this neglect in the race to Mars.  Soviet exploration of the Red
    Planet also suffered from this event, as preoccupation with the
    gathering of Martian soil led to no further Mars expeditions until
    the PHOBOS probes of 1988.

        The VENERA landers did return some useful information, however.
    Surface temperatures were found to be 446 degrees Celsius (835 degrees
    Fahrenheit) for VENERA 11 and 460 degrees Celsius (860 degrees Fah-
    renheit) for VENERA 12.  Eighty-eight Earth atmospheres pushed down
    on VENERA 11, while its counterpart dealt with two more bars of air
    pressure.

        The Soviet mass spectrometers agreed with the PIONEER VENUS
    results on the high amount of argon in the air.  The gas chromato-
    graphs found carbon monoxide for the first time, though this was
    unknown until the data was reanalyzed in 1980.  This same instrument
    on VENERA 11 found only minute traces of atmospheric water, while
    VENERA 12 recorded none.  It was determined that if all the water
    on Venus was pulled down from the sky onto its surface, it would
    make a film across the globe only one centimeter (0.39-inch) thick.
    Venus is a very dry planet, though conditions might once have been
    quite different.

        A puzzling contradiction was made by the X-ray fluorescence
    cloud aerosol analyzer aboard VENERA 12.  In the layers where sulfur
    was expected to be found, large particles of chlorine compounds were
    recorded in their place.  This went against the data from earlier
    spacecraft missions and Earth-based observations.  Future probes
    with even more sensitive devices would be required to resolve this.

        The spectrophotometers relayed that the clouds were thin enough
    to allow visibility for several kilometers, but the Sun itself would
    be impossible to see from the ground.  The Groza lightning detectors
    seemed to have found widespread electrical activity:  The noise from
    one alleged bolt created thunder which shook around VENERA 12 for
    fifteen minutes.  Early theories associated the lightning with the
    volcanic region the landers had come down upon, as Earth volcanoes
    do sometimes trigger thunderstorms.  However, the readings had taken
    place far above the Phoebe volcanoes, revising the lightning concept
    as being only cloud-to-cloud in nature.  Some scientists argued that
    Venus' atmosphere was too stagnant to produce lightning of any sort,
    leaving the idea of Venerean electrical storms still in doubt.

        PIONEER VENUS 1 and 2 and VENERA 11 and 12 had finally given
    planetary scientists an overall picture of what the second world
    from the Sun was truly like.  There was, however, more than enough
    conflicting and missing information from the probes to warrant new
    missions to root out the details.  Soviet spacecraft engineers
    passed the next launch window in the spring of 1980 to prepare
    a more advanced set of VENERAs for the job.

        Venus in Color

        On October 30 and November 4, 1981, two PROTON rockets lifted the
    VENERA 13 and 14 probes from the Tyuratam Space Center into the skies.
    The new Venus explorers were similar to the 1978 VENERAs, though with
    improved instrumentation and several new additions, including a pene-
    trometer and an X-ray fluorescence spectrometer.  The penetrometer
    would test the density and strength of the soil at the landing sites
    and the spectrometer would analyze the air and soil brought into it
    by the lander's drilling device.  The main buses would also flyby
    Venus instead of orbiting the planet.

        Released on February 27, 1982 after a four-month interplanetary
    trajectory, the VENERA 13 lander descended towards Venus, entering the
    top of its atmosphere on March 1.  During its sixty-two minute trek
    to the surface, the lander's aerosol X-ray fluorescence spectrometer
    found an abundance of sulfur over chlorine, the opposite of VENERA
    12's findings and in agreement with earlier observations.

        The spectrophotometer reported that the cloud base ended at forty-
    nine kilometers (twenty-nine miles) above the ground, with three main
    layers found along the way to the base.  The Groza 2 lightning instru-
    ment recorded weak radio noises, leading some scientists to conclude
    that the probe had detected its own electrical charging through the
    air, rather than any native thunderstorms.

        VENERA 13 touched down on the rolling plains of far eastern
    Phoebe Regio.  The surface temperature was a very warm 465 degrees
    Celsius (869 degrees Fahrenheit) and air pressure was 89.5 times
    that of Earth's at sea level.  The lander communicated with its
    controllers for 127 minutes, still the record for contact by a
    craft on Venus' surface.

        As an improvement over the picture-taking of VENERA 9 and 10 in
    1975, VENERA 13 and its twin carried two cameras with red, blue, and
    green filters.  The arrangement allowed for the first color images
    of Venus' surface in eight panoramas from around the entire craft.

        This innovation did not disappoint.  The planet was bathed in
    orange light from the bright daytime sky, contrasting with the blue
    sky of Earth and the pink one of Mars.  The ground appeared similar
    to the image taken at Beta Regio by VENERA 10, with slabs of rock
    embedded in dark soil.  The horizon could be seen in the pictures.
    Across the bottom of the images was the landing torus with its test
    patterns and jutting triangular "teeth".  These teeth helped keep
    the lander steady during its descent to the planet.  Also visible
    was a color scale, the penetrometer, and the ejected camera covers.
    Loose soil was seen blowing onto the torus from winds moving at one
    to two kilometers (0.6 to 1.2 miles) per hour.

        During its brief lifetime, the VENERA 13 lander performed a
    successful drilling of the surface to a depth of three centimeters
    (1.2 inches).  The soil sample was brought into the craft and
    irradiated for analysis by the X-ray fluorescence spectrometer,
    where it was found to be similar to leucitic basalt on Earth, a
    rare basalt on this planet with high potassium and magnesium levels.
    The lander's seismometer recorded no venusquakes while the probe was
    active.

        The VENERA 14 lander descended upon western Navka Planitia on
    March 5, about one thousand kilometers (six hundred miles) southeast
    of VENERA 13.  The landing site was a hill five hundred meters (1,650
    feet) high but still lower than the VENERA 13 area, judging by the
    air pressure measurement of 93.5 Earth atmospheres and a temperature
    of 470 degrees Celsius (878 degrees Fahrenheit).  A bright orange sky
    was evident in the eight panoramas returned, but the surface appeared
    more weathered and covered in slabs of rock, with several foothills

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End of Space Digest Volume 16 : Issue 289
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