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
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.
History of the space exploration of Venus:
 Sputnik 7 represents the first (Soviet’s)
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.
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.
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 craft’s travel to Venus.
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.
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 craft’s closest approach
 no magnetosphere
 First atmospheric measurements: mainly
CO2 and detection of a continuous cloud
cover without any breaks and a cloud top
altitude of about 60 km.
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.
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.
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
inclination between 88° and 99°, which is very useful to obtain a maximum view on
Earth and thus it is often used for espionage satellites.
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.
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.
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 craft’s journey to
the planet (like Zond 1).
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.
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
that it did not exceed 0.0003-times the magnetic field of
the Earth at its surface.
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 flyby’s 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.
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 Earth’s 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.
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.
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
6050 ± 5 km.
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.
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
the assumed composition of the near pancake-structure (Basilevsky et al., 1991, 1992, 1997).
 The light level at the surface was found to be similar to the amount of illumination in
Moscow at noon on an overcast winter day with a visibility of about 1 km.
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.
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
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.
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).
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
basaltic lava
History of the space exploration of Venus:
PV surface map of Venus:
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
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.
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).
 The soil sample was again found to be similar to oceanic tholeiitic basalts.
History of the space exploration of Venus:
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 planet’s
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).
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 Sun’s 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.
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.
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.
Summarizing the previous landing-sites:
Summarizing the previous landing-sites:
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