1 . A planet that suffers 475 C beneath a thick acid atmosphere may be the last place you'd expect alien (外星的) life in our solar system. But one NASA scientist claims that extraterrestrials (天外来客) are most likely hiding on Venus amid conditions that are unbearable for humans. The new theory was put forward by the research scientist Dr Michelle Thaller. She says that possible signs of life have already been seen within the carbon-dioxide filled atmosphere, adding that she was absolutely certain that life exists somewhere.

Venus is often described as Earth's twin due to its similar size and structure. But their conditions couldn't be further apart, as astronomers believe it would be impossible for humans to exist on Venus. Positioned 67 million miles from the Sun, Venus is the hottest planet in our solar system, suffering temperatures that can even melt lead. Its atmosphere also adds to the uninhabitable situation.

Despite this, scientists have long debated whether Venus' clouds may host microbial (微生物的) life forms that can survive. Many scientists think that photosynthesis (光合作用) is possible on the planet's surface as Venus receives enough solar energy to pass through its thick clouds.

However, Professor Dominic Papineau, a biologist at the University College of London, believes Dr Thaller's views are “difficult to realistically assume”. He explained, “For life-related chemical reactions to take place, liquid water is necessary. Hence, to find extraterrestrial life, we need to find liquid water, and to find extraterrestrial fossils requires looking for special rocks that were associated with liquid water in the past.”

This makes life on Venus today difficult to realistically assume, because its surface is too hot, although Venus might have had liquid water in its past. Even still, both Professor Papineau and Dr Thaller agree that the icy moons of our solar system could also be sites of potential microbial life. NASA suggests there are 290 “traditional moons” in our solar system-excluding 462 smaller minor planets.

2 . Even though they may appear to be completely unrelated, black holes and Las Vegas have one thing in common: Whatever happens there stays there, much to the displeasure of astrophysicists who are trying to understand how black holes grow.

The event horizon can be conceptualized as an outer ring that surrounds black holes and is the boundary beyond which nothing, including matter, light, or information, may pass. It takes in every bit of evidence about the black hole’s past and has the appearance of being “stuck” to the eyes of an observer.

“Because of these physical facts, it had been thought impossible to measure how black holes formed,” said Peter Behroozi, an associate professor at the University of Arizona Steward Observatory.

Behroozi co-led an international team to rebuild the growth histories of black holes using machine learning and supercomputers, successfully avoiding the event horizon information barrier for individual black holes to show what is beyond. Millions of artificial universes were simulated (模拟), and the results showed that supermassive black holes grew at the same pace as their host galaxies (星系). Scientists had a theory about this for 20 years, but had not been able to confirm this relationship until now. The team’s research was reported in a publication in Monthly Notices of the Royal Astronomical Society.

“As the galaxy grows from small to large, its black hole, too, is growing from small to large, in exactly the same way as we see in galaxies today all across the universe,” Behroozi said.

Trinity is a platform developed by the researchers that uses a novel type of machine learning to generate millions of different universes on a supercomputer. The goal of Trinity is to find answers. The project’s three main research areas are galaxies, their supermassive black holes, and their dark matter halo (晕). The same Trinity is in inference to these three areas. Millions of galaxies and their dark matter halo were simulated using the researchers’ older University Machine in past investigations.

The researchers found that galaxies expanding in their dark matter halo have a very particular relationship between the galaxy’s mass and that of the halo.

3 . The combined quantity of water on Earth has varied over the course of our planet’s geological history, and it still does.

Today, Earth includes some 1,386 million cubic kilometres of water, a volume that includes water in oceans, lakes and rivers, plus ground water, vapour in the atmosphere, and the frozen water of glaciers and ice caps. On the young Earth — some four billion years ago — vast quantities of water were added to the planet by ice-containing comets (a mass of ice and dust that moves around the sun and looks like a bright star with a tail) that struck us, eventually making our world a “blue planet”. But such events became increasingly rare in Earth’s more recent history, and today we are in an age during which Earth is losing water.

The water loss is due to the fact that particles (微粒) sometimes escape Earth’s gravity to travel into space. This is particularly true of the light hydrogen atoms that form part of water molecules (分子) together with oxygen. Every time the atmosphere loses hydrogen, we lose one of the building blocks of water. Scientists estimate that Earth loses about 3kg of hydrogen per second. At this pace, Earth would run out of water in three billion years — but that assumes that we don’t get any new water supplies.

New water need not come from space — it might come from the inside of the Earth. At depths below 50km, minerals contain water that is not reckoned within the water cycle. Some of it dates back to Earth’s formation; the rest is part of slow geological exchange between the planet’s layers. When Earth’s plates sink and melt, deep minerals can release these bound water molecules so that they can subsequently rise to the surface via volcanic eruptions, adding to the planet’s overall water resources.

4 . The lander carrying China’s first Mars rover successfully touched down on the red planet early Saturday morning Beijing Time. It is the first time China has landed a probe on a planet other than Earth.

Tianwen-1, consisting of an orbiter, a lander and a rover, was launched from the Wenchang Spacecraft Launch Site on the coast of southern China’s island province of Hainan on July 23, 2020. This is the first step in China’s planetary exploration of the solar system, with the purpose of completing orbiting, landing and roving on the red planet in one mission.

The name Tianwen, meaning “questions to Heaven”, comes from a poem written by the ancient Chinese poet Qu Yuan (about 340-278 BC). China’s first Mars rover is named Zhurong after the god of fire in ancient Chinese mythology, which echoes with the Chinese name of the red planet: Huoxing (the planet of fire).

Tianwen-1 was launched via a Long March-5 rocket, China’s largest launch vehicle. Tianwen-1 has been traveling in space for nearly 10 months. It has carried out four orbital corrections and a deep-space maneuver. It had flown 475 million km and was 192 million km from Earth when it reached Mars orbit.

The craft’s plummet through the Martian atmosphere, lasting about nine minutes, was extremely complicated with no ground control, and had to be performed by the spacecraft autonomously.

“Such a challenging attempt is characterized by a succession of complex activities that must be conducted completely by the spacecraft within a very short period of time,” said Geng Yan, an official with the Lunar Exploration and Space Program Center of the CNSA. “What added to the difficulties was that we don’t know much about the Martian atmosphere, which brought a lot of uncertainties to the mission. Each step had only one chance, and the actions were closely linked. If there had been any flaw, the landing would have failed.”