Venus Flashcards
whats is the mass of venus compared to earth?
0.82 x
what is the radius of venus compares to earth?
0.95 x
what is the surface gravity of venus compared to earth?
0.9 x
what is the mean orbital radius?
0.72 au , almost circular
what is the maximum elongation of venus?
48 degrees from sun as seen from earth
what is the albedo?
76%, brightest object in sky after sun and moon
does venus have phases?
yes, bigger than mercurys’ and can be seen with binoculars.
what phase of venus is the brightest?
crescent
when is venus visible?
evening or morning.
rotation period of venus?
ranges from 22 hours up to 224.7 days
what did photographic observations show in 1950s?
a y shaped feature gave a 4 day retrograde (reverse) rotation.
what did radar measurements show in 1961?
surface rotated in a period of 243 days and was retrograde
why does venus have a high albedo?
clouds of venus reflect sunlight
what did spectroscopic measurements in 1930 show?
CO2 major constituent
what did radio observations show?
that surface temp is hot about 500 degrees
what is the composition of the atmosphere?
96% carbon dioxide 3.5% nitrogen traces of so2 water vapor h20 sulphuric acid h2s04 (acid rain)
what is the temp at the cloud tops?
-30 degrees
what is the pressure at the surface?
90 atmospheres
what distances do the sulfuric acid clouds form?
between 48-60 km from ground
how is the expected temperature calculated?
Tplanet = TSun (1 − a)^0.25√RSun/2d
Tplanet= expected temp in kelvin of planet d= distance from sun a= albedo (a=1 then 100% reflection)
why is venus much hotter?
green house gases
visible light penetrates clouds and gets to surface- warmed and re-radiates in the infrared.
re-radiated energy is absorbed and heat is trapped near surface
what did mariner 10?
flyby photos of cloud tops taken in ultraviolet showed rapidly moving circulation, only 4 days to circle planet speeds of 360 km/h- retrograde direction
what did veneras do?
beneath clouds, landing probes on surface
what did veneras find out?
hostile planet 90x pressure that earth at sea level landscape- heap of stones- sharp edges and smooth wind speeds sluggish sunlight casts shadows
what did the pioneer venus orbiter do?
moniter cloud motions, while probes recorded data on temp, pressure and composition with altitude
what did the magellan do?
detailed radar map of entire surface- no magnetic field
what did venus express do and when launched?
nov 2005
arrived april 2006
found evidence for past oceans and confirmed presence of lightning by studying atmosphere and clouds
what did venera 9 show?
scree on a hill (15-25 degrees) slope, field of flat boulders,separated by sharp stones and dust
what did venera 10 show?
older more weathered, smoother surface
gamma ray spectrometer revealed volcanic rock, basalt
what did venera 13 show?
phoebe regio: rock-strewn plain, with outcrops and patches of dark, fine-grained material.
evidence of chemical erosion.
soil showed basalt and potassium
what did venera 14 show?
less-fine grained material
regular layers of rocky,broken plates
basalts similar to earths seabed
average density of venus?
5.3 g/cm^3
which features reflect better?
a hard flat surface better than powdered one
earth facing slope better than oblique
what was the pioneer venus the first to attempt 1978?
orbit radar around venus
how did the pioneer venus take its recordings?
using radar altimeter which bounced microwaves off surface. Built up a map in strips as venus rotated. mapped 93% of surface- resolution of 50km
what are the 3 general types of terrain on venus?
1: rolling plains (65%)
2: highlands (8%)
3: lowlands (27%)
Describe features of rolling plains
lying within 500m of mean level, numerous craters and circular basins, some filled with lava.
Some volcanic, some impact
large and shallow.
what are the three major regions of highlands?
ishtar terra, aphrodite terra, beta regio
what are the features of ishtar terra?
size of australia. lofty plateau (3km). several mountains, including maxwell montes which is highest of venus volcanic region
what are the features of aphrodite terra?
size of africa, rough and broken mountains
what are the features of beta regio?
two large shield volcanoes, rhea and theia mons. 4km high and lie on fault line.
what do the valley and trench systems imply?
tectonic activity played a role in formation of these regions
why does water vapour increase green house gases on venus compared to earth?
no seas to dissolve co2 it in.
what did eventually happen with the water?
dissociated into hydrogen which escapes and oxygen which reacted with rocks
what is a transit of mercury and venus?
because closer to sun, get between earth and sun on occasion and can be seen as dark discs moving across solar surface
why is there more opportunities to see a transit of mercury?
orbits the sun more quickly
why does the geometric alignment of mercury only occur every 7 years in may or november?
the plane of mercurys orbit is tilted by 7 degrees with respect to that of earth
what is the orbital plane of venus with respect to earths orbit?
inclined by 3.4 degrees so takes 8 years in pairs in june or december, each pair separated by 106 or 121 years
what can transits be used for?
to measure parallax angle
