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Earth and Venus, what is the link?

The four terrestrial planets, in true colors and to scale

Figure 1 :  The four terrestrial planets of our inner Solar System: Mercury, Venus, Earth and Mars. These images were taken by the Mariner 10, Apollo 17 and Viking missions. ©ESA

In the table below, the similarities (left hand side) point towards similar formation conditions. Scientists widely believe the two planets formed in very comparable regions of the protoplanetary disk and evolved in parallel, at least at the beginning. However, many fundamental characteristics (right hand side) are completely opposite.
These similarities and differences are key to understanding the evolutionary pathways of terrestrial planets. Increased knowledge on present and past geophysical processes will provide insight on how terrestrial planets form and differentiate.

 

Venus

Earth

 

Venus

Earth

Distance from Sun

0.72 AU

1AU

Rotation period

243 Earth days (retrograde)

23 hours 56 minutes

Surface gravity

0.91g

1g

Surface temperature

465 deg Celsius

15 deg Celsius

Orbit period

224.7 days

365.2 days

Surface pressure

90 bar

1 bar

Orbit inclination

3.4 degrees

0 degrees by definition

Atmosphere

96% CO2, 3% N2

78% N2, 21% O2

Density

5250 kg/m3

5520 kg/m3

Moons

None

1

Radius

6052 km

6378 km

Magnetic field

Very weak/ Unknown

Strong/ Dynamo driven


Venus and other Earths

Venus and Earth alongside Exoplanets, artist impression

Figure 2 :  Venus, our most Earth-like neighbour, compared to artist impressions of two recently discovered exoplanets

Studying Venus is a necessary prerequisite to better understanding our Earth – and the other similar exoplanets. While the next few years promise to bring an unprecedented harvest of potentially habitable exo-Earths, data acquired at Venus will be invaluable in classifying them and understanding their complexity. Furthermore, Venus’ unique vantage point in our Solar System will make it possible to better constrain the inner edge of the habitable zone (also known popularly as the goldilocks region).

Venus Earth and Mars as the spectrum of their atmospheres could be seen from another solar system

Figure 3 :  Spectra from different Earth-like planets. Of the four terrestrial planets in our Solar System (Mercury, Venus, Earth and Mars) the last three possess atmospheres. These are the kinds of spectra we would expect when searching for Earth-like planets in other solar systems. ©ESA 2001. Illustration by Medialab.

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