Venus Landing-Sites

1
Venus Landing-Sites Where we have been and
where we want to go
J. J. Leitner, Dept. of Astronomy, Univ. of
Vienna, Austria
1st VEP Landing-Sites Workshop, November 14-15,
2006, Vienna, Austria
2
Venus before the space-age

• In 1961, before the first spacecraft reached
  Venus, different
• descriptions about planet Venus exist in
  literature (Colin, 1983)
• Cool, Earth-like, with surface water and a dense
  atmosphere, or
• Cold, polar regions with 10-km-thick icecaps and
  a hot equatorial region with
• temperatures far above the water boiling
  point, or
• A moist, swampy and teeming with life planet, or
• Warm, encased by a global carbonic acid ocean,
  or
• Warm, massive clouds consisting of water and
  intensive lighting, or
• Hot and dusty, dry, windy, a global dessert, or
• Extremely hot, cloudy, molten lead and zinc
  puddles at the equator, seas of
• bromine, butyric acid and phenol at the poles.

?
3
History of the space exploration of Venus

• Sputnik 7 represents the first (Soviets)
• approach to send a spacecraft to Venus
• (with the goal to impact on the
• planetary surface)
• Successfully launched into Earth orbit in
• Feb. 1961 (a launch platform and the probe).
• Probably due to a faulty timer, the probe
• remained in Earth orbit and never starts
• towards Venus.
• Originally it was thought to be Venera 1, but
  due
• to its failure the name Sputnik was given.

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History of the space exploration of Venus

• Venera 1, launched 8 days later, was intended
• to fly-by Venus.
• 7,500,000 km away from Earth, the contact
• with the probe was lost.
• It is assumed that the probe flyby Venus at a
• distance of 100,000 km, but no data were
• returned.
• Payload magnetometer (operates during the
• first days), micrometeorite detectors, ion
  traps
• cosmic radiation counters.

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History of the space exploration of Venus

• Mariner 1, launched in July 1962, was the first
  U.S. mission to Venus.
• 290 seconds after its launch the probe was
  destroyed by the mission command,
• because of a trajectory error and the chance
  to crash into an inhabited area
• on Earth.
• Payload microwave and infrared
• radiometer, a magnetometer, an
• electrostatic analyzer and two
• instruments to investigate the cosmic
• dust and the cosmic ray ionization
• during the crafts travel to Venus.

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History of the space exploration of Venus

• Sputnik 19, a Venera-like spacecraft was
  launched in August 1962 and was
• intended to be Venera 2.
• It was designed to land on the
• surface of Venus.
• Due to a technical fault in the escape
• stage from the launch rocket, the
• probe remained in Earth orbit and
• burned out in the atmosphere.

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History of the space exploration of Venus

• Mariner 2, launched in August 1962, was the
  first successful planetary
• exploration probe (at all, not only for Venus)
  and performed a Venus flyby mission.
• After a 109 days lasting journey the probe
  flybys Venus at a distance of 34,833 km.
• It measured the radiation temperature of small
  areas of Venus in a region between
• 200 K and 600 K in two different wavelengths.
• By orbit tracking of Mariner 2 the value
• for the Venusian mass was improved.
• Most important scientific discovery
• complete absence of charged particles
• associated with the planet at a distance
• of the crafts closest approach
• ? no magnetosphere
• First atmospheric measurements mainly
• CO2 and detection of a continuous cloud

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History of the space exploration of Venus

• Sputnik 20, was launched in September 1962 and
  was concepted as a
• Venus landing mission.
• It endured the same fate than Sputnik 19 and
  reenters Earth atmosphere
• 5 days after its launch.
• Because of the mission
• design and its purpose
• it is very probable, that
• the craft was intended
• to be second probe of
• the Venera series.

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History of the space exploration of Venus

• Sputnik 21, was also launched in September 1962
  (11 days after Sputnik 20)
• and was an attempted Venus flyby mission.
• It was destroyed in Earth orbit, after the third
  rocket stage exploded.

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History of the space exploration of Venus

• Cosmos 21, presumably was a technology test for
  the Venera series, or (and
• this is up to now not known) an attempted
  Venus flyby mission.
• It was successfully launched into Earth orbit in
  November 1963, but for whatever
• reasons it never left it.
• It is known that the designation Cosmos since
  the beginning of 1963 was
• given to spacecrafts, which remained in Earth
  orbit regardless their originally
• scheduled destinations (e.g. engine burn
  problems).
• But the Cosmos designation was also used for
  spacecrafts, which had only
• military tasks or served as communications
  satellites. As a consequence of this,
• it was easy for the mission control to veil
  the original function of a craft by the use
• of the Cosmos name (a tactic of blur, which
  was often used in the era of the cold war).
• Today it is assumed that about 50 of all the
  Cosmos crafts (more than 2300)
• had been used from the former Soviets military
  for their purposes.
• A clue for this assumption is that nearly all of
  the Cosmos crafts had an orbit

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History of the space exploration of Venus

• Venera 1964A and Venera 1964B (launched in
  February and March 1964) were
• planned as a bipartite Venus flyby mission.
• Due to faults in their launching phases, the
  crafts were destroyed and did never
• reach Earth orbit.
• Cosmos 27 presumably likewise was projected as a
  Venus flyby mission, which
• already reached successfully Earth orbit but
  did never start to Venus.
• Presumably it was a new try to make Venera 2.

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History of the space exploration of Venus

• Zond 1 reached successfully Venus after its
  launch in April 1964.
• The contact with the spacecraft was lost in May
  1964.
• The official mission aims were ultraviolet
• observations of Venus and space
• research consisting of measurements of
• the energetic particles in the interplanetary
• medium and to perform tests of the probe
• systems with the ulterior motivation to
• improve the Venera space mission designs.

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History of the space exploration of Venus

• The real Venera 2, launched in November 1965
  passed the planet Venus
• in February 1966 at distance of 24,000 km.
• Unfortunately the communication systems
• of the probe had already stopped to work
• before the probe the planet was reached.
• The main mission task was to obtain photos
• from the Venusian surface after performing
• a soft-landing.
• But at least after a long series of mission
• faults, a Soviet spacecraft had arrived
• again at Venus.
• The only data returned to Earth were
• measurements about the energetic
• particles during the crafts journey to
• the planet (like Zond 1).

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History of the space exploration of Venus

• Venera 3 (also launched in November 1965) main
• mission task also was to land on the surface
  of
• Venus, but the communication with the probe
  was
• lost shortly before it started to descent the
  atmosphere.
• Nevertheless Venera 3 was the first spacecraft,
  which
• impacted on the surface of another planet.
• Cosmos 96 probably was intended as a Venus
  lander of similar design than
• Venera 3. It reached successfully Earth orbit,
  but an explosion after the
• separation phase from the rocket body finished
  the plan to execute the first
• successful soft-landing on the Venusian
  surface.
• Presumably this mission was part of a bipartite
  mission together with Venera 1965A,
• which was launched three days later, but not
  successful due to a fault in the
• launching phase.

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History of the space exploration of Venus

• Venera 4 (launched in June 1967) represents the
  first really successful atmospheric
• descent probe. In contrast to its predecessors
  the probes communication systems
• operated accurately all the obtained data were
  transmitted back to Earth.
• Mission aims cosmological investigations during
  its flight, to probe the planetary
• vicinity and to penetrate deep into the
  atmosphere in order to determine its
• physical and chemical characteristics.
• The craft consists of two different parts an
  interplanetary and an descending unit.
• After Venus was reached the two units were
  separated
• and the descent unit began its 93 min lasting
  way
• through the Venusian atmosphere.
• The probe measured at different altitudes the
  pressure and
• the temperature in the atmosphere and
  performed first gas
• analyses. The mean temperature gradient in the
  atm.
• was found to be roughly linear with about 10 K
  km-1.
• Measurements of the magnetic field of the planet
  showed

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History of the space exploration of Venus

• Mariner 5 (launched in June 1967, 2 days
• after Venera 4) was the second NASA
• mission to Venus and flybys it successfully
• at a distance of 3,320 km.
• The craft determined the magnetic field,
• atmospheric turbulences, the interaction of
• the solar wind with the atmosphere and
• the wind velocity.
• A very high concentration of CO2
• (about 90 ) and a content of N2 lower than 10
  was measured.
• In general, Mariner 5 confirms the measurements
  of Venera 4 spacecraft.
• Orbit tracking of the spacecraft allows to
  determine the Venusian
• planetary radius to be between 6079 and
  6105 km, but closer to 6079 km.

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History of the space exploration of Venus

• Cosmos 167, constructed very similar to Venera 4
  was also launched
• in June 1967.
• But as it is the fate of Venus Cosmos missions
  it was damaged in Earth
• orbit and reentered Earths atmosphere 8 days
  after its launch.
• Because of its launch date (5 days after Venera
  4) it seems reasonable, that
• the craft was intended to be a companion of
  Venera 4 with a planned
• designation Venera 5.

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History of the space exploration of Venus

• Venera 5 and Venera 6 (launched in January 1969
  with a difference of 5 days)
• main mission aims of their descent probes was
  to continue the success of
• Venera 4 by obtaining more atmospheric data of
  Venus.
• Their design have been improved (greater
  structural strength, reduced parachute
• area, improved instruments).
• In addition to the measurements also done by
  Venera 4, Venera 5 and 6 also
• measured solar wind fluxes and ions with
  energies greater that 50 eV. The
• probes measured more than 70 times the
  pressure and more than 50 times
• the temperature during their descents and
  determined
• also the atmospheric composition from an
  altitude of
• 55 km down to 19 km.
• Venera 5 returned data from the atmosphere for
  53 min
• and Venera 6 for 51 min. Both missions we owe
  a much
• better knowledge about the composition of the
• atmosphere, better thermal and pressure
  gradients.

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History of the space exploration of Venus

• Venera 7 (launched in August 1970 with a
  difference of 5 days) was regarding
• its design similar to Venera 5 and 6, but
  modified to tolerate a pressure of
• about 180 atm and an outside temperature of
  about 800 K.
• Its main mission goal was to perform a
  soft-landing on the surface.
• The craft entered successfully the atmosphere
  and after a 35 min lasting
• descent (with returned atmospheric data from a
  height of 55 km down to
• the surface) it successfully performed a
  soft-landing on the night side of the
• surface, about 2000 km away from the sunrise
  terminator.
• From its landing area it transmitted back data
  for 23 min,
• which made Venera 7 to the first spacecraft
  that returned
• data from the surface of another planet.
• The temperature was found to be 747 20 K, the
• pressure to be between 86 and 97 atm.
• The improved value for the planetary radius was

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History of the space exploration of Venus

• Cosmos 359 (launched in August 1970), launched 5
  days after Venera 7,
• presumably was scheduled to be Venera 8 with
  the intention to company
• the previous probe.
• Due to a fault in the escape stage of the
  launch-rocket, the engine did not
• last the necessary time to leave Earth orbit
  toward Venus (about 4 min).
• The spacecraft remained in Earth orbit for 410
  days until its orbit decayed and
• the craft burnt up in the terrestrial
  atmosphere.
• By orbit tracking of Cosmos 359 during its
  life-span, valuable information about
• the terrestrial atmospheric rotations speed
  and the atmospheric density
• at altitudes near 200 km was obtained.

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History of the space exploration of Venus

• Venera 8 (launched in March 1972), also executed
  a successful soft-landing on the
• Venusian surface. It transmitted back data
  during its 56 min lasting descent about the
• pressure, temperature and the downward light
  flux from an altitude of 50 km down to
• ground. Thereby it experienced a sharp
  decrease in the illumination level between 35 and
  
• 30 km (maybe as a consequence of different
  amounts of aerosols in the atmosphere).
• Further composition of the atmosphere, cloud
  structure and the cloud layers,
• measurements about aerosols, wind speeds,
  rotation of the upper clouds, etc.
• Its landing-site is dominated by volcanic
  plains, steep-sided domes and shield fields. The
• site is composed of a mosaic of radar-light
  and radar-dark spots, crossed by radar-bright
• lineaments in N-W orientation (open fractures)
  and with a pancake structure at the northern
• edge of the landing-site (Abdrakhimov 2001
  Basilevsky et al., 2001).
• It survived 50 min at the surface and
  transmitted back data about temp., pressure and
• performed the first gamma-ray spectroscopic
  analysis of the surface of another planet.
• Based on this experiment the rocks were
  interpreted to be either alkaline basalts or some
  
• more evolved subalkaline and alkaline
  intermediate rocks (perhaps andesite, trachyte),
• resembling to the composition of terrestrial
  continental crust and in a good agreement with

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History of the space exploration of Venus

• Cosmos 482 (launched in March 1972), was
  originally thought to be Venera 9.
• It was very similar in design to Venera 8, but
  after its successful launch
• into Earth orbit, an error in the launch phase
  (a too short engine burn) let it
• remain in Earth orbit.

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History of the space exploration of Venus

• Mariner 10 (launched in November 1973) primarily
  was a Mercury probe, but
• on its journey to the planet it encountered
  Venus at a distance of 5,768 km.
• It was the first spacecraft that visited two
  planets and thereby used the
• first gravity-assist maneuver.
• The Venus flyby was used to study the ionosphere
  and upper atmosphere for
• a time period of 8 days. It observes emissions
  from the upper atmosphere and
• confirmed the 4-days rotation period of the
  atmosphere.
• Further measurements about thermal emissions of
  
• the atmosphere, interaction between the solar
  wind
• and the atmosphere.
• Orbit tracking

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History of the space exploration of Venus

• Venera 9 and 10 (launched in June 1975) Each
  spacecraft consists of two
• different parts an orbiter and a lander. The
  probes performed similar
• measurements about the atmospheric parameters
  than the earlier Venera probes.
• Venera 9 lands in the Beta regio uprise and
  transmitted back data to Earth for a
• period of 53 min. Thereby the very first photo
  from the surface of another planet
• was received.
• The investigated rocks at this site were very
  shape-edged without features, which
• would indicate the presence of geochemically
  evolved lavas. Due to their shape
• the rocks are called slaps. The adjacent
  surface, in which the rocks were
• ingrained, consists of a fine-grained matrix
  with a very low albedo.
• Gamma-ray spectroscopic measurements indicates
  contents of K, U, Th similar to
• that of tholeiitic basalts on Earth.

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History of the space exploration of Venus

• Venera 10 landed in a distance of about 2,000 km
  away from Venera 9, in the
• southeastern edge of Beta regio. The area is
  dominated by wrinkle-ridged
• plains. Tessera terrain of heavily deformed
  material of unknown nature was
• located close to its landing-site.
• It transmitted back data for 65 min about temp.,
  pressure, one photo and wind
• velocity measurements.
• Venera 10 performed the first direct density
  measurements of Venusian rocks
• ? were found in a good agreement with the
  conception of a basaltic composition
• of the crust (2800 100 km m-3).
• The radioactive contents of the investigated
  rocks were somewhat lower than that
• at the Venera 9 site, but again in a good
  agreement with a basaltic composition
• (in a transitional zone between tholeiitic and
  alkaline basalts).

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History of the space exploration of Venus

• The Pioneer Venus 1 (Orbiter) was launched in
  May 1978) and operated at a
• distance between 150 km and 66,900 km away
  from the Venusian surface.
• One of its main tasks was a radar investigation
  of the surface of the planet and
• the detection of the gravity field. Beside
  this also cloud layers, ionosphere, solar
• wind and atmosphere interaction, magnetic
  field, mass and density distribution, etc.
• ? better models of the interior and
  specification of the amount of isostatic
• compensation of the Venusian topography
  and crust.
• It performed the first radar and altimetry
  mapping of the surface (93 ) with
• resolutions between 150 and 200 m.
• Roughly characterization of the surface
• Uplands, 65 of the surface
• Highlands, 8 of the surface
• three radar-bright extremes
• Ishtar-, Aphrodite- and Beta Regio
• Lowlands, 27 of the surface,
• mainly covered by younger

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History of the space exploration of Venus
PV surface map of Venus
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History of the space exploration of Venus

• Pioneer Venus 2 Multiprobe (launched in August
  1978) consisted of a large
• entry bus, a large probe and three smaller
  probes
• ? allows simultaneous investigations of the
  atmosphere in different areas.
• Measurements about the atmospheric structure,
  composition, particle size,
• radiation, solar flux, winds, turbulences,
  etc.
• The probes did not have parachutes to
• perform a soft landing. Regardless this
• lack one of the probes returned data for
• a period of 67 min after its impact.

Ultraviolet image of Venus cloud patterns
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History of the space exploration of Venus

• Venera 11 and 12 (launched in September 1978,
  with a delay of 5 days)
• consisted again of an orbiter and
  descent/landing unit.
• Measurements about the solar wind composition,
  observation of gamma-ray bursts,
• investigation of the ultraviolet radiation and
  the electron and proton density in the
• ionosphere of Venus.
• Studies of the characteristics and the
• composition of the atmosphere
• ? Detection of a very high 36Ar/40Ar ratio,
• and evidences for lighting and thunder.
• After their soft-landing the probes transmitted
• back for 95 and 110 min, but unfortunately
• some instruments fail (no pictures were
• returned to Earth, if they have carried
• cameras, not really known, because in the
• Soviet literature there are no clues about it.

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History of the space exploration of Venus

• Venera 13 and 14 (launched in October/November
  1982, with a delay of 5 days)
• consisted again of an orbiter and
  descent/landing unit.
• The probes performed similar measurements than
  the earlier Venera probes,
• but had working imaging systems. The landers
  carried along x-ray spectrometer
• and instruments to perform chemical, isotopic
  and mechanical measurements
• of surface samples.
• Venera 13 returned data for 127 min, the
  landing-site at all was similar to that of
• Venera 10. Taken soil samples manifest
  themselves as weakly differentiated
• melanocratic alkaline gabbroid with high MgO,
  a low silica and with a content of
• about 4 K2O.
• The load capacity of the soil was found to be
  between 2.6 and 10 kg cm-2.
• Venera 14 lands on a basaltic plain and about
  800 km southeast of Venera 13.
• Its site is dominated by lava flows arising
  from the nearby volcano with lengths
• between tens and hundreds of kilometers
  (Basilevsky et al., 1992).

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History of the space exploration of Venus
32
History of the space exploration of Venus

• Venera 15 and 16 (launched in June 1983, with a
  delay of 5 days) were each
• part of a common Venus radar mapping mission
  to study the surface properties
• of the planet.
• Together they imaged about 25 of the planets
• surface, but offers in contrast to Pioneer
• Venus also images of the northern
• polar region consisted again of an orbiter
• and descent/landing unit.
• From the available data more than
• 150 impact craters have been identified.
• First identification of Corona structures
• (clues were available also from PV).

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History of the space exploration of Venus

• Vega 1 and 2 (launched in December 1984, with a
  delay of 6 days) primarily
• were designed to investigate comet Halley,
  which in 1986
• returned to the Suns environment during its
  76 years period.
• The Venusian experiments were executed from two
  balloons
• (at similar latitudes north and south of the
  equator), which
• were ejected by the Vega crafts. During the
  descent of the
• balloons, their courses were tracked for 47
  hours
• ? good record of the atmospheric winds and
• gusts along them atmospheric parameters
• have been determined.
• Small landers were dropped out, which
  successfully
• reached the surface and confirms in the first
  line the
• older measurements.
• X-ray spectrometer and mass spectrographs,
• but no imaging systems.

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History of the space exploration of Venus

• NASA Magellan (launched in May 1983) was
  implemented to obtain detailed
• knowledge about the Venusian surface and its
  mechanisms.
• The mission offered a nearly global radar
  imaging survey of the surface with a very
• high resolution and high accuracy gravity
  data. Its radiometer allowed to obtain
• temperature, pressure and density values of
  the whole atmosphere.
• At the end of the mission 98 of the surface
  have been mapped and gravity data
• for 95 of the planet were available.
• Large number of different structures have been
  discovered based on its datasets.
• Up to now the Magellan datasets are the basis
  for any work related to the surface
• of Venus.

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History of the space exploration of Venus
Hemispheric view of Venus (produced by Magellan)
After Magellan only flybys have taken place until
2006 (Cassini, Galileo) (as VEX reached Venus),
but no other Venus missions were performed.
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Summarizing the previous landing-sites
37
Summarizing the previous landing-sites
38
VEP landing-sites
Main question now Where to go with the VEP
descent probes? To which structures, altitudes,
etc. Only two restrictions at the moment 3
dayside, 1 nightside (close to antisolar
point) wide latitudinal distribution