New research explains how Earth became a habitable planet
Earth has a large amount of water and a relatively large moon, which stabilizes Earth’s axis. Both are essential for life to develop on our planet. Scientists have now been able to show that water came to Earth with the formation of the moon.
The Earth is unique in our solar system: It is the only terrestrial planet with a large amount of water and a relatively large moon, which stabilizes the Earth’s axis. Both were essential for Earth to develop life.
Planetologists at the University of Münster (Germany) have now been able to show, for the first time, that water came to Earth with the formation of the Moon some 4.4 billion years ago. The Moon was formed when Earth was hit by a body about the size of Mars, also called Theia. Until now, scientists had assumed that Theia originated in the inner solar system near the Earth. However, researchers from Münster can now show that Theia comes from the outer solar system, and it delivered large quantities of water to Earth. The results are published in the current issue of Nature Astronomy.
From the outer into the inner solar system
The Earth formed in the ‘dry’ inner solar system, and so it is somewhat surprising that there is water on Earth. To understand why this the case, we have to go back in time when the solar system was formed about 4.5 billion years ago. From earlier studies, we know that the solar system became structured such that the ‘dry’ materials were separated from the ‘wet’ materials: the so-called ‘carbonaceous’ meteorites, which are relatively rich in water, come from the outer solar system, whereas the drier ‘non-carbonaceous’ meteorites come from the inner solar system. While previous studies have shown that carbonaceous materials were likely responsible for delivering the water to Earth, it was unknown when and how this carbonaceous material — and thus the water — came to Earth.
“We have used molybdenum isotopes to answer this question. The molybdenum isotopes allow us to clearly distinguish carbonaceous and non-carbonaceous material, and as such represent a ‘genetic fingerprint’ of material from the outer and inner solar system,” explains Dr. Gerrit Budde of the Institute of Planetology in Münster and lead author of the study.
The measurements made by the researchers from Münster show that the molybdenum isotopic composition of the Earth lies between those of the carbonaceous and non-carbonaceous meteorites, demonstrating that some of Earth’s molybdenum originated in the outer solar system. In this context, the chemical properties of molybdenum play a key role because, as it is an iron-loving element, most of the Earth’s molybdenum is located in the core.
“The molybdenum which is accessible today in the Earth’s mantle, therefore, originates from the late stages of Earth’s formation, while the molybdenum from earlier phases is entirely in the core,” explains Dr. Christoph Burkhardt, second author of the study. The scientists’ results therefore show, for the first time, that carbonaceous material from the outer solar system arrived on Earth late.
But the scientists are going one step further. They show that most of the molybdenum in Earth’s mantle was supplied by the protoplanet Theia, whose collision with Earth 4.4 billion years ago led to the formation of the Moon. However, since a large part of the molybdenum in Earth’s mantle originates from the outer solar system, this means that Theia itself also originated from the outer solar system. According to the scientists, the collision provided sufficient carbonaceous material to account for the entire amount of water on Earth.
“Our approach is unique because, for the first time, it allows us to associate the origin of water on Earth with the formation of the Moon. To put it simply, without the Moon there probably would be no life on Earth,” says Thorsten Kleine, Professor of Planetology at the University of Münster
Kepler-186f, the First Earth-size Planet in the Habitable Zone
A newly discovered planet nicknamed “Earth’s cousin” has just been found 490 light-years from Earth.
The planet, called Kepler-186f, is the first Earth-size planet found in the habitable zone of its star. Only about 10 percent larger than Earth, Kepler-186f is the closest planet to Earth in size ever found in the habitable zone of its star. What else do you need to know about the new alien planet discovery?
Here are five things to keep in mind about Kepler-186f:
Kepler-186f is the first Earth-size alien planet found in the habitable zone of its star. That means the planet, which is only slightly larger than Earth, is in the part of its star system where liquid water could exist on the planet`s surface.
Astronomers have found other planets in the habitable zones of their stars, but this is the first time a planet this close in size to Earth has ever been found in the habitable zone of its star.
“This is an historic discovery of the first truly Earth-size planet found in the habitable zone around its star,” University of California, Berkeley astronomer Geoff Marcy, who is unaffiliated with the new research, said. “This is the best case for a habitable planet yet found. The results are absolutely rock solid. The planet itself may not be [rocky], but I’d bet my house on it. In any case, it’s a gem.”
Scientists discovered the planet in data collected by NASA’s Kepler space telescope.
Life could thrive … maybe
Because of Kepler-186’s location in the habitable zone around its star, the planet might be a place where life can thrive. It’s possible that the planet has an atmosphere that can help keep water in liquid form on the surface, a prerequisite for life as it is known on Earth.
Kepler-186f is on the outer edge of the habitable zone, so it is possible that the planet’s water could freeze. Its larger size, however, could mean the planet has a thicker atmosphere, insulating the planet, San Francisco State University astronomer and study co-author Stephen Kane said in a statement.
Although they know the alien world is in its star’s habitable zone, scientists still aren’t sure what the planet’s atmosphere consists of, and they cannot say with certainty that Kepler-186f could support life. The planet is Earth-sized, but it might not be Earth-like.
“Some people call these habitable planets, which of course we have no idea if they are,” Kane said in a statement. “We simply know that they are in the habitable zone, and that is the best place to start looking for habitable planets.”
It is one of five planets in the Kepler-186 star system
Kepler-186f is one of five planets found in the extrasolar system located about 490 light-years from Earth. The newly discovered exoplanet orbits about 32.5 million miles (52.4 million kilometers) from its sun. It takes Kepler-186f about 130 days to orbit its red dwarf star.
The other four planets orbiting the star, however, are not in that “Goldilocks zone.”
“The four companion planets — Kepler-186b, Kepler-186c, Kepler-186d and Kepler-186e — whiz around their sun every four, seven, 13 and 22 days, respectively, making them too hot for life as we know it,” NASA officials said in a statement. “These four inner planets all measure less than 1.5 times the size of Earth.” [10 Exoplanets That Could Host Alien Life]
The broadly accepted theory for the origin and evolution of our universe is the Big Bang model, which states that the universe began as an incredibly hot, dense point roughly 13.7 billion years ago. So, how did the universe go from being fractions of an inch (a few millimeters) across to what it is today?
Here is a breakdown of the Big Bang to now in 10 easy-to-understand steps.
Step 1: How It All Started
The Big Bang was not an explosion in space, as the theory’s name might suggest. Instead, it was the appearance of space everywhere in the universe, researchers have said. According to the Big Bang theory, the universe was born as a very hot, very dense, single point in space.
Cosmologists are unsure what happened before this moment, but with sophisticated space missions, ground-based telescopes and complicated calculations, scientists have been working to paint a clearer picture of the early universe and its formation.
A key part of this comes from observations of the cosmic microwave background, which contains the afterglow of light and radiation left over from the Big Bang. This relic of the Big Bang pervades the universe and is visible to microwave detectors, which allows scientists to piece together clues of the early universe.
In 2001, NASA launched the Wilkinson Microwave Anisotropy Probe (WMAP) mission to study the conditions as they existed in the early universe by measuring radiation from the cosmic microwave background. Among other discoveries, WMAP was able to determine the age of the universe — about 13.7 billion years old.
Step 2: The Universe’s First Growth Spurt
NASA, ESA, and S. Beckwith (STScI) and the HUDF Team
When the universe was very young — something like a hundredth of a billionth of a trillionth of a trillionth of a second (whew!) — it underwent an incredible growth spurt. During this burst of expansion, which is known as inflation, the universe grew exponentially and doubled in size at least 90 times.
“The universe was expanding, and as it expanded, it got cooler and less dense,” David Spergel, a theoretical astrophysicist at Princeton University in Princeton, N.J., told SPACE.com.
After inflation, the universe continued to grow, but at a slower rate. As space expanded, the universe cooled and matter formed.
Step 3: Too Hot to Shine
Light chemical elements were created within the first three minutes of the universe’s formation. As the universe expanded, temperatures cooled and protons and neutrons collided to make deuterium, which is an isotope of hydrogen. Much of this deuterium combined to make helium.
For the first 380,000 years after the Big Bang, however, the intense heat from the universe’s creation made it essentially too hot for light to shine. Atoms crashed together with enough force to break up into a dense, opaque plasma of protons, neutrons and electrons that scattered light like fog.
Step 4: Let There Be Light
About 380,000 years after the Big Bang, matter cooled enough for electrons to combine with nuclei to form neutral atoms. This phase is known as “recombination,” and the absorption of free electrons caused the universe to become transparent. The light that was unleashed at this time is detectable today in the form of radiation from the cosmic microwave background.
Yet, the era of recombination was followed by a period of darkness before stars and other bright objects were formed.
Step 5: Emerging from the Cosmic Dark Ages
ESA XMM-Newton/EPIC, LBT/LBC, AIP
Roughly 400 million years after the Big Bang, the universe began to come out of its dark ages. This period in the universe’s evolution is called the age of re-ionization.
This dynamic phase was thought to have lasted more than a half-billion years, but based on new observations, scientists think re-ionization may have occurred more rapidly than previously thought.
During this time, clumps of gas collapsed enough to form the very first stars and galaxies. The emitted ultraviolet light from these energetic events cleared out and destroyed most of the surrounding neutral hydrogen gas. The process of re-ionization, plus the clearing of foggy hydrogen gas, caused the universe to become transparent to ultraviolet light for the first time.
Step 6: More Stars and More Galaxies