September 10, 2019
Published by Kshitij Kumar
Presently we have very less information regarding the type of minerals that might be found inside the Moon. But a group of researchers from Canada and the US has used this hint to understand that a treasure is lying beneath the surface.
By getting more information about the chemistry of the moon, scientists would be able to settle a confusion regarding the apparent lack of precious elements constituting the mantle of Moon. Nearly fifty years ago, astronauts brought back a large quantity of lunar material which gave the first hints about the elements that might be present below the surface. James Brenan, Earth scientist from Dalhousie University, Canada said that nearly 400 kilograms of the sample was brought in the Apollo and lunar missions. So to find about the Moon’s interior, scientists have to go through reverse-engineering of the composition of lavas on the surface.
Through retro-engineering the basalts which were brought from the Apollo 15 and 17 missions, researchers estimated the amount of siderophile elements which make up the mantle of Moon. Some of these might have come from the rain of leftover materials in the finishing stages of the Solar System’s construction, so it can tell the assault endured by the Moon after its formation was complete. The work appears in Nature Geoscience journal.
The measurements were lower by 10 to 100 times than what was expected. Even by adjusting the model to accommodate the event of erosion of Moon by the meteorites, the numbers did not add up which left a plethora of questions. Researchers often begin by assuming the geochemistry of Moon to be similar to Earth and this is where the gaps in the measurement start. Although several theories suggest that Moon was made from Earth’s components there are some notable differences.
Hence researchers used the experiment results on sulfur solubility with the models on pressure and the thermodynamics of magma cooling down to get accurate constraints on the composition of the lunar mantle. Brenan said that the results tell that sulfur in the volcanic rocks of Moon indicates the presence of iron sulfide in the Moon’s rocky interior. This is the place where the metals might have been during the formation of lavas.
The results make it clear that we cannot depend on the existing rock samples for any clear conclusion as no accurate estimation of metal composition cannot be found. Whether it would be justified for mining these metals would depend on future missions and economics. But this makes the return to Moon quite exciting.
Research Paper: Abundance of highly siderophile elements in lunar basalts controlled by iron sulfide melt
August 8, 2019
Published by Kalpit Veerwal
Ancient water drops might have changed the timeline of the Earth’s tectonic plates as researchers have analyzed a series of drops from ancient seawater and arrived at an estimate that the process which underpins the plate tectonics of the Earth might have started 600 million years earlier than previously considered. The study has been published in Nature journal.
The constant movement of tectonic plates is a crucial part of renewing the surface of the planet and flourishing of life. By analyzing the levels of water in microscopic melt inclusions trapped in volcanic rock sample called komatiites, researchers calculated a new timeline when the seawater got pushed down from surface to the mantle, the point when convection started to occur. The ancient water droplets were captured in the mineral olivine found in the komatiites from the Komatiite lava flow which remained after the hottest magma was produced in Archaean Eon.
Geologist Alexander Sobolev from the Russian Academy of Sciences said the mechanism that caused the crust to sink into the mantle started 3.3 billion years ago. A global cycle of the matter was established within the first billion years and the excess water in mantle’s transition zone came from the ancient oceans.
Factors like atmospheric conditions and minerals deposited underground have been affected by shifting of the Earth’s plates along with the earthquakes and volcanoes. The plate tectonics always recycles the matter on Earth without which our Earth would end up looking like Mars. Plate tectonics started 3.3 billion years before which coincides with the time life began on Earth.
The geological landscape which was formed by these tectonic movements provides an excellent record of what happened in the past. The komatiite was dug up from Weltevreden Formation in the Barberton greenstone belt in South Africa.
After examining the piece of melt of close to 10 microns and analyzing the chemical indicators like water content, chlorine and hydrogen/deuterium ratio, it was found that the Earth’s recycling process started close to 600 million years earlier than what was thought initially. It was found that the seawater was transported deep into the mantle and later re-emerged through volcanic plumes from the core-mantle boundary.
The chemical signature of the lithographic mantle matches with that of the analyzed rocks from the Archaean, despite coming from further down in the transition zone between upper and lower mantle. The komatiites grabbed so much water from deep underground before being shot up to the surface, which in turn indicates that the tectonics plate cycle happened earlier than 2.7 billion years ago which is the currently accepted starting point. The chemical mixes, pressure, geological processes have many variations to account in the readings. More research is needed to figure out exactly when the material of the Earth’s crust started shifting.
Journal Reference: Nature
June 2, 2019
Published by Kalpit Veerwal
As per the reports of a new study by a team of geoscientists from Macquarie University, Sydney, salt traces trapped in many diamonds reveal on analysis that the stones are produced from the seabeds which have been trapped inside the Earth’s crust for countless years.
A majority of the diamonds which are found on the surface of the Earth are formed in this manner while the others are formed due to the melt crystallisation quite deep in Earth’s mantle. In the experiments, researchers from Goethe Universität and Johannes Gutenberg Universität of Germany simulated the high pressures and temperatures which exist 200 kilometres deep inside the Earth. They found that the seawater which is present in the sediment at the ocean’s bottom reacts in the right way to form the salts which are present in the diamonds.
The study has been published in the journal Science Advances and it clears a major confusion about the way diamonds are formed. It was earlier thought that the salts within diamonds originated from the marine seawater. However, the research cleared that they originated from the marine sediment.
Diamonds are classified into gem diamonds and fibrous diamonds. Gem diamonds are fully composed of carbon in its purest form while fibrous diamonds contain the traces of elements such as sodium, potassium which can disclose a lot of information about the conditions in which their formation took place. Fibrous diamonds normally grow faster than gem diamonds which indicates that small samples of fluids are trapped during formation.
Samples of marine sediment were placed inside a vessel containing a rock called peridotite. It is the most common type of rock which is present in the mantle where diamonds are formed. Pressure and heat were increased and the adequate time to react with one another was given matching the conditions of the mantle.
At values of pressure lying between four and six gigapascals and temperatures in the range of 800 degrees to 1100 degree Celsius, which is equivalent to the depth of 120-180 kilometres inside Earth, salts were produced having the balance of sodium and potassium. It matched with the traces that are obtained inside diamonds.
Dr Michael Förster, lead author of the paper remarked that they have successfully demonstrated the sequence of steps which lead to the growth of diamonds and confirmed that the recycling of sediments in the ocean is responsible for it.