The Sirens Of Titan

Where did the Moon come from?

The Moon is about 40 to 140 million years younger than the Earth and its geology offers broad hints that it was formed in an impact. This is called the giant impact hypothesis.

Nobody can be sure what actually happened, but computer simulations provide some clues. In one simulation, the newly-formed Earth suffers an impact with another planet (called Theia, a little larger than Mars). Theia is torn apart, its core dragged down through Earth’s interior to merge with the Earth’s core. Much of Theia’s mantle is absorbed into Earth’s mantle, and the side of Theia furthest away from the impact is hurled into space. About half the material ejected by the collision is lost and the rest accretes to form the Moon.

The Earth’s axis is tilted, and it is left spinning faster than it does today. A day lasts about ten hours. Months are much shorter too, as the new Moon orbits the Earth much faster. It is also much closer. Had there been anyone on Earth to observe it, they would have glimpsed a Moon twice the present size in the Earth’s primitive sky.

The Moon has since slowed the Earth’s spin, and it is moving away from us at a rate of almost 4 centimetres a year.

You can learn more about the birth of our Moon via Origins: The Scientific Story of Creation by Jim Baggott, or by following #BaggottOrigins across social media.

Image: Moon, by Yutaka Tsutano. CC-BY-2.0 via Flickr.

Watch a NASA Spacecraft Touch Down On an Asteroid to Collect a Sample

On Tuesday, NASA’s OSIRIS-REx spacecraft touched down on an asteroid called Bennu for about six seconds in order to collect a mineral sample to bring back to Earth.

The Origins Spectral Interpretation Resource Identification Security - Regolith Explorer spacecraft will travel to a near-Earth asteroid, called Bennu (formerly 1999 RQ36), and bring at least a 2.1-ounce sample back to Earth for study. The mission will help scientists investigate how planets formed and how life began, as well as improve our understanding of asteroids that could impact Earth.

The video above is a time lapse sequence of the touch down, sampling, and subsequent take off.

These images were captured over approximately a five-minute period. The imaging sequence begins at about 82 feet (25 meters) above the surface, and runs through the back-away maneuver, with the last image in the sequence taken at approximately 43 feet (13 meters) in altitude – about 35 seconds after backing away. The sequence was created using 82 SamCam images, with 1.25 seconds between frames.

Neutron Stars and Nuclear Pasta. Yummy!

The latest video from Kurzgesagt is a short primer on neutron stars, the densest large objects in the universe.

The mind-boggling density of neutron stars is their most well-known attribute: the mass of all living humans would fit into a volume the size of a sugar cube at the same density. But I learned about a couple of new things that I’d like to highlight. The first is nuclear pasta, which might be the strongest material in the universe.

Astrophysicists have theorized that as a neutron star settles into its new configuration, densely packed neutrons are pushed and pulled in different ways, resulting in formation of various shapes below the surface. Many of the theorized shapes take on the names of pasta, because of the similarities. Some have been named gnocchi, for example, others spaghetti or lasagna.

Simulations have demonstrated that nuclear pasta might be some 10 billion times stronger than steel.

The second thing deals with neutron star mergers. When two neutron stars merge, they explode in a shower of matter that’s flung across space. Recent research suggests that many of the heavy elements present in the universe could be formed in these mergers.

But how elements heavier than iron, such as gold and uranium, were created has long been uncertain. Previous research suggested a key clue: For atoms to grow to massive sizes, they needed to quickly absorb neutrons. Such rapid neutron capture, known as the “r-process” for short, only happens in nature in extreme environments where atoms are bombarded by large numbers of neutrons.

If this pans out, it means that the Earth’s platinum, uranium, lead, and tin may have originated in exploding neutron stars. Neat!

Strange moons

Earth and Moon

Space Shuttle Endeavour mounted atop one of NASA’s modified Boeing 747 Shuttle Carrier Aircraft.

Ode to Apollo 11 and the joy of discovery

Mountains on the Moon (actually Pluto)

A vintage NASA-commissioned Rick Guidice painting gives a cutaway view of the inside of a space colony design known as the Stanford torus, a proposed habitat that would house 10,000 to 140,000 permanent residents. The rotating, doughnut-shaped ring could have a diameter of around 2 kilometers, revolving once per minute to give about 1.0g of artificial gravity on the inside of the ring through centripetal force. A massive system of mirrors would provide the sunlight needed for daily activity, agriculture, and so forth. (NASA Ames Research Center)