SOLVE magazine Issue 02 2021 | Page 22

Looking to the immediate future , I think we can better constrain the geological timeline for Mars and put some real radiometric age constraints on when things happened on Mars – when volcanism and impacts happened , when surface water disappeared and intertwining that with the search for life .
– James Darling

Messages from time

As our solar system formed , it left telltale messages about long-ago events frozen into the minerals and structure of rock . Space exploration and meteorites provide opportunities to access these time capsules and the knowledge gained builds our understanding of how and when life formed in our solar system .

Here on Earth , strung along

the Orion Arm of the Milky Way galaxy , we are bit by bit coming to know the cosmic order that underlies planetary life . Our solar system is thought to have formed from gravity-driven contraction of interstellar gas and dust into the Sun and planets .
There are , however , periods in this chronology that are murkier than others . Particularly vexing for planetary scientists is a gap covering the first billion years of Earth ’ s history ( 3.5 to 4.5 billion years ago ), when it was evolving the ability to sustain life .
Dr James Darling , who is a Reader in Earth and Planetary Materials at the University of Portsmouth , studies this time period . He says there are answers to be found , but they are hidden within the microscopic features of ancient – and therefore exceptionally rare – rock .
These features can be ‘ read ’ using advanced analytical methods to reveal the forces at play during the rock ’ s formation , including the occurrence of massive impact events , the eruption of volcanoes or the movement of tectonic plates .
These time-machine-like glimpses
into a different era are lacking on Earth , unfortunately , when it comes to the period when life first formed . Dr Darling explains why :
“ The Earth has been resurfaced and reworked by plate tectonics and erosion throughout its history , so the surface we have today is relatively young ,” Dr Darling says . “ In fact , there are very few places on Earth where it ’ s possible to find rocks that are billions of years old .”
Fortunately , this scarcity does not hold true beyond our planet , as researchers learned following the birth of the space age .
“ When the Apollo missions to the Moon brought back rock samples , we started to realise those lunar craters and surfaces were very ancient – billions of years old ,” Dr Darling says . “ So , we can look to other planets – and to planetary fragments in the form of asteroids – to understand the forces that created them and learn a lot about the early Earth .”
That is precisely Dr Darling ’ s speciality : he works up laboratory methods to analyse billion-year-old fragments of rocks sourced from the Moon , asteroids and Mars . These methods typically involve using high-energy light , electron and ion beams to probe mineral structures and chemistry down to the atomic scale . He then combines the results with observational data about the geological features of these extraterrestrial bodies .
Given the relevance of this work to issues around the origins of life , Dr Darling also looks for signatures that can weigh in on another vexing question : whether Earth was alone in being able to evolve a biosphere and living organisms .
He undertakes this work in collaboration with space exploration missions or the museums and agencies that curate extraterrestrial samples , including the Apollo materials ( whose analysis is overseen by NASA ) and meteorites from the Royal Ontario Museum .
The lunar samples continue to reveal the relevance of space exploration to understanding Earth ’ s history , with Dr Darling ’ s group recently discovering that massive impact melt sheets were responsible for forming large portions of the Moon ’ s crust . His team is revving up its efforts and collaborations , with much of the focus shifting to Mars . This is due to the number of missions underway
ISSUE 02 / 2021