The author: Professor Yasser Metwally
Although Mars has grabbed the headlines as a potential site of extraterrestrial life, Venus may have been the original source of life in our solar system, suggests a new book by a University of Colorado astronomer.
Four billion years ago the sun was 40 percent cooler than today. During that time, Earth and Mars probably were frozen. Venus, however, is closer to the sun, and may have had warm liquid oceans and a mild climate at the time, notes CU-Boulder Assistant Professor David Grinspoon of the astrophysical and planetary sciences department.
Video 1. Life on Venus
"There is some reason to believe Venus may have been the best haven for life in the early solar system," he said. With 900 degree Fahrenheit surface temperatures and an atmosphere permeated by carbon dioxide, chlorine and sulfuric acid clouds today, Venus seems inhospitable to "our kind of life," he said. "But we really don’t know much about life — its requirements, it’s differences and how to recognize it."
It is even possbile that life on Earth may have evolved from life forms provided by Venus, Grinspoon said: "Pieces of planets were blasting off of each other all the time early in the evolution of the solar system, and microbes from Venus could easily have wound up on Earth."
While the standard scientific view is that life requires water and carbon-based molecules, it cannot really be said if that is the only chemical system that can make life, said Grinspoon, who has been studying the surface, atmosphere and clouds of Venus for 10 years through NASA-sponsored programs.
Indeed, Venus may have a better environment for nurturing life than Mars, he said. Like Earth, Venus has a chemically lively surface and atmosphere that could provide organisms with energy and nutrients.
"In my view, what makes Earth special is its atmospheric cycles that renew themselves like a garden tilling itself," he said. "It could well be that kind of an environment on Venus is just as important for life as carbon."
Figure 1. The surface of Venus seen by the soviet spacecraft Venerra (Click to enlarge figure)
Because the surface and atmosphere of Venus are constantly renewing themselves through volcanic activity, there is more potential for interesting chemical and even biochemical processes on Venus than on Mars, he said.
"It’s possible that Venus could have tiny microbes in its cloud particles, or that some form of Venusian life could have developed by using ultraviolet light much like Earth’s plants use sunlight to make food. There could even be a non-carbon-based equivalent to lichens atop Venus’ five-mile-high volcanoes, perhaps feeding on sulfur gases," he said.
The interactions of Earth’s oceans, clouds, surface and biosphere has led some scientists to propose "the Gaia theory", that Earth itself is a living system. "By constantly exhaling sulfur gases that react with the clouds and surface minerals, Venus could be considered in that Gaia realm," notes Grinspoon.
Although NASA’s 1989 Magellan probe opened a new window on the planet using sophisticated radar mapping, there is still much to learn about Venus, said Grinspoon. One key is to keep an open mind about chemical and perhaps biological processes that may be occurring there and on other planets.
"Venus is the closest thing Earth has to a twin," he said. "Studying Venus is how we learned about the problem with our ozone layer, and it’s a way for us to become wiser in taking care of our own planet."
Venus is very hot, almost 800 degrees (Fahrenheit) at the surface. Venus also has a very heavy atmosphere. With a heavy atmosphere, there is a lot of pressure (about 91-94 times sea level pressure on Earth). A sophisticated life form such as a human-being would need a heavy shell for protection, just as humans going to great pressures under the sea need a submarine. Venus also has corrosive clouds of sulfuric acid.
We know, however, that there are life forms on earth which can survive in very harsh environments. Bacteria and very simple plant life can survive in unexpected places.
Because of the very high temperature, pressure, and corrosive atmosphere the environment of Venus seems unfriendly toward life as we know it on earth. More exploration of Venus is needed to determine if life was once present there.
The author: Professor Yasser Metwally
Video 1. The Apollo 11 mission landed the first humans on the Moon. Launched on July 16, 1969, the third lunar mission of NASA’s Apollo Program was crewed by Commander Neil Alden Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Edwin Eugene ‘Buzz’ Aldrin, Jr. On July 20, Armstrong and Aldrin became the first humans to land on the Moon, while Collins orbited in the Command Module.
The author: Professor Yasser Metwally
Tycho is a prominent lunar impact crater located in the southern lunar highlands, named after the Danish astronomer Tycho Brahe. To the south is the crater Street; to the east is Pictet, and to the north-northeast is Sasserides. The surface around Tycho is replete with craters of various sizes, many overlapping still older craters. Some of the smaller craters are secondary craters formed from larger chunks of ejecta from Tycho.
Age and Description
Tycho is a relatively young crater, with an estimated age of 108 million years (Ma), based on analysis of samples of the crater rays recovered during the Apollo 17 mission. This age suggests that the impactor may have been a member of the Baptistina family of asteroids, but as the composition of the impactor is unknown this is currently conjecture. However, simulation studies give a 70 percent probability that the crater was created by a fragment from the same break-up that created asteroid 298. a larger asteroid from the same family may have been the impactor responsible for creating Chicxulub Crater on Earth 65 million years ago (mya), and causing the extinction of the dinosaurs.
The crater is sharply defined, unlike older craters that have been degraded by subsequent impacts. The interior has a high albedo that is prominent when the Sun is overhead, and the crater is surrounded by a distinctive ray system forming long spokes that reach as long as 1,500 kilometers. Sections of these rays can be observed even when Tycho is illuminated only by earthlight.
The large ray system centered on TychoThe ramparts beyond the rim have a lower albedo than the interior for a distance of over a hundred kilometers, and are free of the ray markings that lie beyond. This darker rim may have been formed from minerals excavated during the impact.
Its inner wall is slumped and terraced, sloping down to a rough but nearly flat floor exhibiting small, knobby domes. The floor displays signs of past volcanism, most likely from rock melt caused by the impact. Detailed photographs of the floor show that it is covered in a criss-crossing array of cracks and small hills. The central peaks rise 1.6 kilometers above the floor, and a lesser peak stands just to the northeast of the primary massif.
Infrared observations of the lunar surface during an eclipse have demonstrated that Tycho cools at a slower rate than other parts of the surface, making the crater a "hot spot". This effect is caused by the difference in materials that cover the crater.
Panoramic view of Tycho taken by Surveyor 7The rim of this crater was chosen as the target of the Surveyor 7 mission. The robotic spacecraft safely touched down north of the crater in January 1968. The craft performed chemical measurements of the surface, finding a composition different from the maria. From this one of the main components of the highlands was theorized to be anorthosite, an aluminium-rich mineral. The crater was also imaged in great detail by Lunar Orbiter 5.
From the 1950s through the 1990s, NASA aerodynamicist Dean Chapman and others advanced the lunar origin theory of tektites. Chapman used complex orbital computer models and extensive wind tunnel tests to support the theory that the so-called Australasian tektites originated from the Rosse ejecta ray of Tycho. Until the Rosse ray is sampled, a lunar origin for these tektites cannot be ruled out.
This crater was drawn on lunar maps as early as 1645, when Antonius Maria Schyrleus de Rheita depicted the bright ray system.
Video 1. Tycho impact crator on the moon