Ti paternity test fingers Earth Moon's parent

Wolfram-Alpha

Steve Koppes
UChicagoNews

A new chemical analysis of lunar material collected by Apollo astronauts in the 1970s conflicts with the widely held theory that a giant collision between Earth and a Mars-sized object gave birth to the moon 4.5 billion years ago.

In the giant-collision scenario, computer simulations suggest that the moon had two parents: Earth and a hypothetical planetary body that scientists call “Theia.” But a comparative analysis of titanium from the moon, Earth and meteorites, published by Junjun Zhang, graduate student in geophysical sciences at the University of Chicago, and four co-authors indicates the moon’s material came from Earth alone.

If two objects had given rise to the moon, “Just like in humans, the moon would have inherited some of the material from the Earth and some of the material from the impactor, approximately half and half,” said Nicolas Dauphas, associate professor in geophysical sciences at UChicago, and co-author of the study, which appears in the March 25 edition of Nature Geoscience.

“What we found is that the child does not look any different compared to the Earth,” Dauphas said. “It’s a child with only one parent, as far as we can tell.”

The research team based their analysis on titanium isotopes — forms of titanium that contain only slight subatomic variations. The researchers selected titanium for their study because the element is highly refractory. This means that titanium tends to remain in a solid or molten state rather than becoming a gas when exposed to tremendous heat. The resistance of titanium isotopes to vaporization makes it less likely that they would become incorporated by the Earth and the developing moon in equal amounts.

Titanium also contains different isotopic signatures forged in countless stellar explosions that occurred before the sun’s birth. These explosions flung subtly different titanium isotopes into interstellar space. Different objects in the newly forming solar system gobbled up those isotopes in different ways through collisions, leaving clues that let scientists infer where the solar materials including the moon came from.
Planetary DNA

“When we look at different bodies, different asteroids, there are different isotopic signatures. It’s like their different DNAs,” Dauphas said. Meteorites, which are pieces of asteroids that have fallen to Earth, contain large variations in titanium isotopes. Measurements of terrestrial and lunar samples show that “the moon has a strictly identical isotopic composition to the Earth,” he said.

“We thought that the moon had two parents, but when we look at the composition of the moon, it looks like it has only one parent,” Zhang said.

Zhang initially found variations in the titanium isotopic composition between the lunar and terrestrial samples. She then corrected the results for the effects of cosmic rays, which could have changed the titanium isotopic composition of the lunar samples.

The Earth and the moon are constantly bombarded by cosmic rays from the sun and from more distant sources in the galaxy. Earth’s atmosphere and magnetic field prevents most of these rays from reaching its surface, but the moon has no such protection.

“We compared the titanium isotopic composition with samarium and gadolinium since those two systems are very sensitive to the cosmic-ray effect,” Zhang said. The only compositional differences the scientists expected to see in samarium and gandolinium between Earth and moon would be the result of cosmic rays. “We found a very nice linear correlation between titanium and samarium or gadolinium,” she said.

Zhang’s titanium analyses greatly reinforce previous work by other researchers who came to the same conclusion after comparing terrestrial and lunar oxygen isotopes, which are less refractory and thus more likely to gasify during a giant impact than titanium.
Lunar Conundrum

Solving the conundrum of the moon’s origin probably will prove challenging because all of the alternative scenarios for the moon’s formation have drawbacks.

For example, it is possible that even though titanium is refractory, it might still have gasified in the giant impact and then became incorporated into the disk of Earth-orbiting material that developed into the moon. This might have erased the signature of the titanium from Theia, which could explain the UChicago team’s observations. The problem with this scenario is that the disk may have fallen back to Earth if too much material was exchanged between the two bodies.

An old idea, long abandoned, is that the moon arose via fission from a molten, rapidly rotating Earth following a giant impact. This idea explains the similarity between Earth and moon, but how such a large, concentrated mass could spin fast enough to split in two remains problematical.

According to a third scenario, Earth collided with an icy body lacking entirely in titanium. There are no bodies made purely of ice in the solar system, however. “They would always have a significant fraction of solid material, so you would still expect the object to deliver some titanium,” Dauphas said.

It’s also possible that Theia had the same composition as Earth. This is unlikely, however, because of the widely accepted view that the Earth incorporated material over tens of millions of years in collisions with smaller bodies that flew in from different regions of the developing solar system.

“We thought we knew what the moon was made of and how it formed, but even 40 years after Apollo, there is still a lot of science to do with those samples that are in curatorial facilities at NASA,” Dauphas said.

Did the Moon come from Earth?

During the 1970's, scientists proposed that an object the size of Mars could have collided with Earth and thrown enough matter into orbit to create the Moon [Don Davis / The New Solar System].

Kelly Beatty
Sky & Telescope

"New findings show that Earth and the Moon have identical isotopic ratios of tungsten — and that's a problem for the widely accepted "big splat" hypothesis."

Read the full article HERE.

ESRF X-rays illuminate lunar interior

Image of artificial moon rock sample, measuring about half
millimeter across, made with an electron microprobe at ambient
temperature after the experiment with X-rays. The fragmenta-
tion of the sample occurred when it was extracted from the
small diamond cylinder in which it had been melted under high
pressure and temperature [ESRF/Nature].

Does the Moon still have even a small, warm liquid core? The answer can only be apparent indirectly, behind its dance movements and the combined angular momentum of it juggled components; the Moon’s anisotropy. If, as investigators now claim, the Moon’s outer surface is still shrinking or, in some cases, stretching, other outward evidence of even a small warm and liquid core can only be discovered indirectly. Why, for example, is any evidence of volcanism on the Moon’s surface at least a billion years old?

A science team in the Netherlands claims to have discovered one answer, the natural buoyancy of molten but poorly mixed constituent materials closer to the Moon’s core. The world’s press is reporting their more subtle investigation, using X-rays, with headlines about future lunar volcanism, which contrasts with their own press release and it's secondary headline:

Deep lunar magma is too heavy to produce active volcanoes

"Scientists have now identified a likely reason for this peaceful surface life: the hot, molten rock in the Moon's deep interior could be so dense that it is simply too heavy to rise to the surface like a bubble in water. For their experiments, the scientists produced microscopic copies of moon rock collected by the Apollo missions and melted them at the extremely high pressures and temperatures found inside the Moon. They then measured their densities with powerful X-rays. The results are published in the Journal Nature Geosciences on 19 February 2012.

"The team was led by Mirjam van Kan Parker and Wim van Westrenen from VU University Amsterdam and comprised of scientists from the Universities of Paris 6/CNRS, Lyon 1/CNRS, Edinburgh, and the European Synchrotron Radiation Facility (ESRF) in Grenoble.

Exploded schematic of the high-pressure cell
assembly for the ESRF synchrotron  X-ray
experiment. The artificial moon rock samples
(orange) were placed inside the ring-shaped, natural
diamond sample holder (grey), and surrounded by
a large disk-shaped container (red) [ESRF/Nature].

"The driving force for vertical movement of magma is the density difference between the magma and the surrounding solid material, making the liquid magma move slowly upwards like a bubble. The lighter the liquid magma is, the more violent the upward movement will be.

"To determine the density of lunar magma, Wim van Westrenen and his colleagues synthesised moon rock in their laboratory in Amsterdam, using the composition derived from Apollo samples as their “recipe”. The pressures and temperatures close to the core of the Moon are more than 45,000 bar and about 1500 degrees. It is possible to generate these extreme conditions with small samples, heating them with a high electric current while squashing them in a press. By measuring the attenuation of a powerful synchrotron X-ray beam at the (European Synchrotron Radiation Facility) in Grenoble, traversing the sample both solid and molten, the density at high pressure and high temperature could be measured.

 “We had to use the most brilliant X-ray beam in the world for this experiment because the magma sample is so tiny and confined in a massive, highly absorbing container. Without a bright beam of X-rays, you cannot measure these density variations”, says Mohamed Mezouar from the ESRF.

"The measurements at the ESRF were combined with computer simulations to calculate the magma density at any location in the Moon.

"Nearly all the lunar magmas were found to be less dense than their solid surroundings, similar to the situation on Earth. There is one important exception: small droplets of titanium-rich glass first found in Apollo 14 mission samples produce liquid magma as dense as the rocks found in the deepest parts of the lunar mantle today. This magma would not move towards the surface.

"Such titanium-rich magma can only be formed by melting titanium rich solid rocks. Previous experiments have shown that such rocks were formed soon after the formation of the Moon at shallow levels, close to the surface. How did they get deep into the mantle? The scientists conclude that large vertical movements must have occurred early in the history of the Moon, during which titanium-rich rocks descended from near the surface all the way to the core-mantle boundary. “After descending, magma formed from these near-surface rocks, very rich in titanium, and accumulated at the bottom of the mantle – a bit like an upside-down volcano. Today, the Moon is still cooling down, as are the melts in its interior. In the distant future, the cooler and therefore solidifying melt will change in composition, likely making it less dense than its surroundings. This lighter magma could make its way again up to the surface forming an active volcano on the Moon – what a sight that would be! – but for the time being, this is just a hypothesis to stimulate more experiments”, concludes Wim van Westrenen."

Reference: Mirjam van Kan Parker, et al., Neutral buoyancy of titanium-rich melts in the deep lunar interior, Nature Geoscience advanced online publication, 19 February 2012

New map of lunar titanium and Iron presented

The above image accompanying many reports of the LROC titanium and iron survey is everywhere being misidentified as showing the boundary area between Mare Serenitatis and Tranquillitatis. It's not clear why Figures 1 - 4 listed along with the official conference news posting were apparently not released at the news conference reported below. The image above may be a part of a larger global mosaic and looks suspiciously like early WAC color test articles released by LROC more than a year ago. Regardless, the area shown in the image above is interesting enough but shows an area mostly south of the equator and southwest of Copernicus on the Moon's nearside.

Map showing concentration of iron and titanium in Nearside maria. Iron and titanium are part of the mineral ilmenite (FeTiO3 ), which has the ability to capture and retain gases, such as hydrogen and helium, from the solar wind. An isotope of helium, helium-3, can be found in ilmenite and is especially valuable for nuclear power production [NASA/USGS/Community College of Baltimore County].

Paris (AFP) — A new map of the Moon has revealed an abundance of titanium ore that is up to 10 times richer than on Earth, a finding that could one day lead to a lunar mining colony, astronomers said on Friday.

The discovery was made thanks to a camera aboard the US Lunar Reconnaissance Orbiter, which swept the surface of the Moon, scrutinizing it in seven different light wavelengths.

Mark Robinson of Arizona State University, who presented the research at a conference in Nantes, western France with Brett Denevi of Johns Hopkins University in Baltimore, sifted through the data for telltale jumps in the ratio of ultra-violet to visible light.

NASA/USGS/Community College of Baltimore County

They established this signature thanks to rock samples brought back to Earth by Apollo 17 astronauts in 1972 and images of the area around the mission's landing site by the Hubble space telescope.

"Looking up at the Moon, its surface appears painted with shades of grey, at least to the human eye," explained Robinson.

"But with the right instruments, the Moon can appear colorful.

"The maria [lunar plains] appear reddish in some places and blue in others.

"Although subtle, these color variations tell us important things about the chemistry and evolution of the lunar surface. They indicate the titanium and iron abundance, as well as the maturity of a lunar soil."

Titanium is as strong as steel but nearly half as light, which makes it a highly desired -- and also very expensive -- metal.

On Earth, titanium is found, at the very most, in around one percent of similar types of ore. But the new map found abundances in the lunar maria that range from about one percent to 10 percent, the conference organizers said in a press release. In the lunar highlands, abundance was around one percent.

The meeting gathers, for the first time, members of the European Planetary Science Congress and the American Astronomical Society's Division for Planetary Sciences.

The find offers a double potential bounty, they said.

"Lunar titanium is mostly found in the mineral ilmenite, a compound containing iron, titanium and oxygen," they said.

"Future miners living and working on the Moon could break down ilmenite to liberate these elements.

"In addition, Apollo data shows that titanium-rich minerals are more efficient at retaining particles from the solar wind, such as helium and hydrogen. These gases would also provide a vital resource for future human inhabitants of lunar colonies."

The exposed upper 3 centimeters surface of the Moon is turned over, or "gardened" at least once every 2 million years. The visible surface has been estimated to reach "optical maturity," or "OMAT," over the course of 900 million years. Direct and remote examination has confirmed that the Moon's deeper topography retains a high-fidelity record of it's stormy 4.74 billion year history, recording the history of the Solar System and Earth while a continuous make over by solar radiation and heavier elements implanted by cosmic ray bombardment. The abundance of Helium-3 and Helium 4 is thought to be related to the abundance of iron and titanium. From: "Global inventory of Helium-3 in lunar regoliths estimated by a multi-channel microwave radiometer on Chang'E-1," WenZhe Fa and Yaqiu Jin (2010), Chinese Science Bulletin, Vol. 55, No. 35 [Maurice Collins].