From today, the Earth is around 60 million years older—and so is the Moon

June 10, 2014, European Association of Geochemistry
Mosaic of the near side of the moon as taken by the Clementine star trackers. The images were taken on March 15, 1994. Credit: NASA

Work presented today at the Goldschmidt Geochemistry Conference in Sacramento, California shows that the timing of the giant impact between Earth's ancestor and a planet-sized body occurred around 40 million years after the start of solar system formation. This means that the final stage of Earth's formation is around 60 million years older than previously thought.

Geochemists from the University of Lorraine in Nancy, France have discovered an isotopic signal which indicates that previous age estimates for both the Earth and the Moon are underestimates. Looking back into "deep time" it becomes more difficult to put a date on early Earth events. In part this is because there is little "classical geology" dating from the time of the formation of the Earth – no rock layers, etc. So geochemists have had to rely on other methods to estimate early Earth events. One of the standard methods is measuring the changes in the proportions of different gases (isotopes) which survive from the early Earth.

Guillaume Avice and Bernard Marty analysed found in South African and Australian quartz, which had been dated to 3.4 and 2.7 billion years respectively. The gas sealed in this quartz is preserved as in a "time capsule", allowing Avice and Marty to compare the current isotopic ratios of xenon, with those which existed billions of years ago. Recalibrating dating techniques using the ancient gas allowed them to refine the estimate of when the began to form. This allows them to calculate that the Moon-forming impact is around 60 million years (+/- 20 m. y.) older than had been thought.

Previously, the time of formation of the Earth' s atmosphere had been estimated at around 100 million years after the . As the atmosphere would not have survived the Moon-forming impact, this revision puts the age up to 40 million years after the solar sytem formation (so around 60 million years older than previously thought).

According to Guillaume Avice: "It is not possible to give an exact date for the formation of the Earth*. What this work does is to show that the Earth is older than we thought, by around 60 my.

"The composition of the gases we are looking at changes according the conditions they are found in, which of course depend on the major events in Earth's history. The gas sealed in these quartz samples has been handed down to us in a sort of "time capsule". We are using standard methods to compute the age of the Earth, but having access to these ancient samples gives us new data, and allows us to refine the measurement".

The xenon gas signals allow us to calculate when the atmosphere was being formed, which was probably at the time the Earth collided with a planet-sized body, leading to the formation of the Moon. Our results mean that both the Earth and the Moon are older than we had thought".

Bernard Marty added: "This might seem a small difference, but it is important. These differences set time boundaries on how the planets evolved, especially through the major collisions in deep time which shaped the ".

Explore further: Scientists may have identified echoes of ancient Earth

More information: *The oldest rocks of the solar system have been dated to 4,568 my ago, so the Earth is younger than that.

The Goldschmidt Conference is the world's leading annual conference on geochemistry. It takes place in Sacramento, California from 8-13 June 2014.

Presentation: The age of the Earth-Moon system revisited using xenon isotope systematics:
Recently, xenon trapped in fluid inclusions of Archean samples from North Pole, Pilbara (Australia) was found to be isotopically intermediate between cosmochemical endmembers (chondritic or solar) and the atmosphere [1, 2]. These results have been interpreted as resulting from prolonged loss of Xe atoms from the atmosphere to the outer space, that lasted at least until the end of the Archean eon [3]. Archean samples analysis together with modeling could help to put further constraints on the early history of the Earth-Moon system. We have analyzed noble gases (Xe, Kr and Ar) in fluid inclusions contained in quartz veins from the Barberton greenstone belt (South Africa) in order to (i) check if this noble gas fractionation represents, or not, a worldwide signature of the Archean atmosphere, (ii) get a more precise isotope analysis of Archean noble gases, and (iii) investigate the Xe isotopic evolution through geological periods of time. The Archean (≈3.2 Ga) Xe isotope ratios, analyzed with a permil precision, indicate an isotopic fractionation of 1.0 ± 0.1 %.amu-1 in favor of the lighter isotopes for the Archean atmosphere relative to the modern one. These results confirm the fractionated state of the archean atmospheric xenon, as a result of prolongated Xe escape from the atmosphere through time. A model has been built to reproduce the temporal evolution of the isotopic composition of atmospheric xenon after a major impact and to take into account the addition of radiogenic/fissiognic Xe atoms from extinct radioactivities (129I, 244Pu and 238U). It permits to put constraints on the I-Pu- Xe age of the Earth-Moon system. The model reproduces with <1% the Xe isotopic compositions of the Archean and the modern atmospheres. It also resolves the unexplained atmospheric under-abundance of Xe isotopes from the fission of 244Pu. When corrected for prolonged loss, I-Pu-Xe ages of the Earth-Moon system are reconciled and shift from 70-100 Ma as previously thought, to 40±20 Ma after CAI.

Related Stories

Scientists may have identified echoes of ancient Earth

June 9, 2014

A group of scientists believe that a previously unexplained isotopic ratio from deep within the Earth may be a signal from material from the time before the Earth collided with another planet-sized body, leading to the creation ...

How many moons does Venus have?

April 23, 2014

There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth's Moon to those with an atmosphere (most notably, Saturn's Titan). Jupiter and Saturn have many moons each, and even Mars has ...

Moon is younger than first thought

September 25, 2013

Improved age data for the Moon suggests that it is much younger than previously believed according to scientists presenting at a Royal Society discussion meeting entitled Origins of the Moon this week (23 September). Professor ...

Recommended for you

NASA powers on new instrument staring at the Sun

March 16, 2018

NASA has powered on its latest space payload to continue long-term measurements of the Sun's incoming energy. Total and Spectral solar Irradiance Sensor (TSIS-1), installed on the International Space Station, became fully ...

Dawn reveals recent changes in Ceres' surface

March 15, 2018

Observations of Ceres have detected recent variations in its surface, revealing that the only dwarf planet in the inner solar system is a dynamic body that continues to evolve and change.


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jun 10, 2014
" this revision puts the age up to 40 million years after the solar sytem formation",
Would that be the moment nuclear fusion began, or some other definition?
5 / 5 (2) Jun 11, 2014
Okay, so there are methods that put the Moon formation early @ ~ 40 Myr and late @ ~100 Myr

This is a radiometric clock at the core. [Abstract] Notably, the first robust dating of the Tellus-Theia collision making Earth-Moon was instead using highly siderophile elements (HSEs) to constrain the evolution of the late accretion. ["Highly siderophile elements in Earth's mantle as a clock for the Moon-forming impact", Jacobson et al, Nature 2014] That puts it late, at 95 +/- 32 million years after condensation of the systems' first solids.

They say on radiometric methods: "Second, reconciling a late Moon-forming event with radiometric chronometers that suggest the opposite result may require challenging fundamental assumptions, such as envisioning a Moon-forming event that did not reset all clocks simultaneously and left significant parts of the mantle non-equilibrated with the core."

5 / 5 (2) Jun 11, 2014
Just this week such a result was presented, on observed mantle heterogenities of Earth:

"""But we believe that the impact energy was not evenly distributed throughout the ancient Earth. This means that a major part of the impacted hemisphere would probably have been completely vaporized, but the opposite hemisphere would have been partly shielded, and would not have undergone complete melting."

The team said that the impact did not completely stir the mantle, ..."
[ http://www.univer...t-earth/ ]

A casino bar. A planet rests his large moon against the disk. He quips: "Shaken. Not stirred." [/Earth. Our Earth.]

@erdave: Good question! FWIW, the siderophile dating paper use "condensation of the systems' first solids", which is a geologically compliant dating (first solids) and used by most.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.