[ad_1]
As our discoveries of exoplanets continue to increase (we have found More than 11,000 possible exoplanets So far) we need to understand whether an Earth-sized planet is more likely to look like Earth or Venus. “We don’t know which of these results is expected or possible,” said Paul Byrne, a planetary scientist at North Carolina State University. In order to discover this, we need to understand Venus better.
Most scientists will agree that any habitable exoplanet needs water.
The surface temperature is 471 °C, and the surface pressure is 89 times lower than that of the Earth. Therefore, it seems impossible that water once existed on Venus. But Venus and Earth are roughly the same size and age, and our best guess is that they are made of similar materials and have very similar starting conditions at birth. Venus is 30% closer to the sun than Earth is. This is important, but not absolutely true. However, after 4.5 billion years, the two planets behaved very differently.
In fact, there is growing evidence that Venus may have water long ago. The pioneer Venus mission launched in 1978 made some tantalizing measurements of the deuterium-hydrogen ratio in the atmosphere, showing that Venus lost a lot of water over time. But we have never had a suitable task to study the history of water on Venus, look for ancient water flow characteristics on the surface, or understand whether it has the geological and climatic conditions essential for water and habitability.
DAVINCI+’s associate principal researcher Giada Arney said: “In our solar system, there may be two habitable worlds side by side. The time is unknown.” Although Venus is not habitable today, the fact that it may be habitable at some point implies However, if the situation is a little better, it is not always destined to suffer such a hellish fate.
This is good news for how we evaluate distant exoplanets. “Looking beyond the solar system, this may also indicate that habitable planets are more common than we previously expected,” Ani said.
There are two main theories about what happened on Venus-they both have an impact on what we might expect of other exoplanets. First of all, consistent with our current but limited observations, Venus has been a mess from the beginning and never let up. Look, the closer the planet orbits its host star, the slower it spins (even the tide locks on one side permanently facing the star, just like the moon revolves around the earth).
Slow-rotating people like Venus are generally more difficult to maintain a cool and comfortable global climate-for a while, it was thought that this might be the reason why Venus became hot and unbearable. The sun’s rays bombard the planet with heat, and the steam-rich atmosphere has never condensed into liquid water on the surface. At the same time, carbon dioxide, water and sulfur dioxide in the air act as greenhouse gases and can only absorb all the heat. It has remained in this state for 4 billion years, whether it is giving or receiving.
Then there are new theories recently developed by Michael Wei and others at NASA’s Goddard Institute for Space Research. The model shows that if you make some small adjustments to the climate of these planets, they can form hemispherical clouds that always face the host star. Reflects a lot of stellar heatAs a result, planets like Venus remain mild, and the vapor in the atmosphere condenses into a liquid ocean on the surface. Way’s work shows that once this point is reached, as long as plate tectonics (which help remove carbon dioxide from the atmosphere) and other earth-like processes can reduce the accumulation of greenhouse gases, the earth can self-regulate its temperature.
This is a complex assumption, full of warnings. If Venus proves that slow-rotating people can develop more livable conditions, then it also proves that these conditions are fragile and may be fleeting.Those who agree with the Way model believe that there are a lot of things that can happen on Venus Volcanic activity Carbon floods the earth and makes the carbon dioxide content in the atmosphere reach 96%, overwhelming everything that the relief plate structure can provide.
However, this is a hypothesis that deserves to be tested by DAVINCI+ and VERITAS, because, as Arney pointed out, many of the potentially habitable exoplanets we find are slow-rotating bodies orbiting low-mass stars. Because these stars are faint, planets must usually come close to them to receive enough heat to form liquid water. If they form hemispherical clouds, they may be able to maintain a habitable climate. The only way we can currently explore whether this hypothesis makes sense is to first see if it might happen on Venus.
But before we apply Wei’s model to other exoplanets, we need to determine whether it can explain Venus. DAVINCI+ will descend to Venus and directly detect the chemical composition and composition of the atmosphere, and will image the surface during the descent. It should be able to collect data types that help tell us whether Venus was really wet early in its life, and enrich its more climatic history and whether it really formed a hemispherical cloud.
The VERITAS orbiter will ask about the geology of the planet and obtain high-resolution images through radar observations, which may be able to detect evidence of terrain or landforms caused by currents or past structures. Perhaps the most exciting target is tessera: a heavily deformed plateau region, considered to be the oldest geological feature on earth. If VERITAS finds evidence of ancient oceans — or at least evidence of geological activity that could have kept the Earth a long time ago — it will support the idea that other slowly rotating exoplanets can achieve the same conditions.
Lauren Jozwiak, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, is working on the VERITAS mission. He said: “Considering that they work together really makes it a complementary large-scale mission. “The idea that you want to conduct geological mapping and atmospheric exploration at the same time has always been the core of Venus you want to investigate,” Jozwiak said.
In the end, if Venus is always uninhabitable, the reason may be related to its proximity to the sun. Therefore, any exoplanet of similar size that is proportionally close to its own star may be like Venus. We’d better focus more research on exoplanets that are farther away from the star.
On the other hand, if Venus has a period of coolness before turning into a permanent oven, it means that we should take the “Venus zone” exoplanets seriously because they may still be habitable. It also shows that factors such as plate tectonics and volcanic activity play a key role in regulating livable conditions, and we also need to find ways to investigate these things in the distant world.
The more we think about what DAVINCI+ and VERITAS can achieve, the more we seem to underestimate how excited we should be. Jozwiak said that these next missions will “completely change our overall view of the formation of Venus and planets.” “This is an exciting time to determine whether Venus is the’earth of the past and future.'”
[ad_2]
Source link
