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Because Venus is completely covered in clouds, human knowledge of surface conditions was largely speculative until the space probe era. Until the mid-20th century, the surface environment of Venus was believed to be similar to Earth, hence it was widely believed that Venus could harbor life.
Planetary habitability in the Solar System is the study that searches the possible existence of past or present extraterrestrial life in those celestial bodies. As exoplanets are too far away and can only be studied by indirect means, the celestial bodies in the Solar System allow for a much more detailed study: direct telescope observation, space probes, rovers and even human spaceflight.
At least two-thirds of Mars' surface is more than 3.5 billion years old, and it could have been habitable 4.48 billion years ago, 500 million years before the earliest known Earth lifeforms; [4] Mars may thus hold the best record of the prebiotic conditions leading to life, even if life does not or has never existed there. [5] [6]
This week, explore the technology that could allow humans to live on Mars, uncover the truth of a Neanderthal flower burial, see a leggy birdlike dinosaur, and more.
Mars, by contrast, is nearly (or perhaps totally) geologically dead and has lost much of its atmosphere. [51] Thus it would be fair to infer that the lower mass limit for habitability lies somewhere between that of Mars and that of Earth or Venus: 0.3 Earth masses has been offered as a rough dividing line for habitable planets. [52]
In addition, humans would not require pressurized suits when outside, merely air to breathe, protection from the acidic rain and on some occasions low level protection against heat. Alternatively, two-part domes could contain a lifting gas like hydrogen or helium (extractable from the atmosphere) to allow a higher mass density. [15]
One major resource issue is how to provide enough oxygen for the Mars-base crew to breathe. NASA is planning to land a crew on the Moon by 2024, and then onward to Mars, possibly in the 2030s. ...
Humans that leave the familiarity of Earth could morph into a separate species. "These people will become an offshoot of the human tree," Impey said in the interview. "They will probably evolve ...