New MIT researchfocusing on the gravitational signature of craters on the far sideof the Moon is shedding light on the nature and origin of the LateHeavy Bombardment (LHB), as well as the earliest life-supportingprocesses that took place in our solar system.
The research drew ondata from NASA's twin Gravity Recovery and Interior Laboratory(GRAIL) spacecraft. The GRAIL mission mapped the gravitationalprofile of around 1,200 craters on the Moon's far side byobserving the push and pull between the spacecraft as they passedover the lunar surface.
The team from MIT thensubjected the data to Bouger correction, a process that removed thegravity readings created by mountains, valleys and other surfacefeatures. This left only gravitational readings taken from within theMoon's crust, allowing the researchers to determine whether impactsduring the LHB and after had the effect of increasing or decreasingporosity.
According to theresults of the study, the upper crust of the lunar highlands, one ofthe most ancient areas on the Moon, was completely pulverized duringthe LHB, an epoch that occurred roughly 3.9 billion years ago and lasted between 20 to 200 million years, and which saw the solar system subjected to anintense barrage of asteroid impacts.
This period ofbombardment opened up great fractures in the Moon's surface and madethe crust extremely porous. Surprisingly, the data also appears toshow subsequent impacts having the reverse effect of reducing theporosity of Earth's closest companion.
The researchersdetermined that asteroids around 30 m (100 ft) in size had pummeled theupper layer of the Moon's crust, known as the megaregolith, punishingit to the extent that while further impacts may have slightly increased ordecreased porosity, the average consistency of the layer could not begreatly altered. In contrast deeper layers of the crust were not sobadly damaged, meaning that their porosity could still be altered bylarger impacts.
By observing suchstructural characteristics on the Moon that stem from the LHB,researchers could potentially gain insights into the processessurrounding the creation of early life in our solar system.
"The whole process ofgenerating pore space within planetary crusts is critically importantin understanding how water gets into the subsurface," statesresearch scientist Jason Soderblom, of MIT’s Department of Earth,Atmospheric and Planetary Sciences. "On Earth, we believethat life may have evolved somewhat in the subsurface, and this is aprimary mechanism to create subsurface pockets and void spaces, andreally drives a lot of the rates at which these processes happen. The Moon is a really ideal place to study this."
Furthermore, bystudying the gravity signatures of larger subsurface craters, theresearchers believe that they may in the future be able to ascertainthe origin of the LHB, settling the argument as to whether theimpactors came from the colossal asteroid belt surrounding our solarsystem, or if they invaded from even farther away.
A paper on the findingshas been published in the online journal Geophysical ResearchLetters.
Source: MIT
