The Last Green Leaf

Eight ridiculous days in 2032:

Two asteroids had impacted Earth seventeen hours apart. Evaluation of the first put it at about the size of a 20-story office block, with an energy capacity close to 50 megatons. Smashing into the Gran Chaco National Park close to the border of Paraguay and Bolivia, it instantly obliterated nearly every country in South America, other than some Pacific coastal regions.

These were soon devastated by tsunamis striking the continent after the second asteroid smashed into the Atlantic Ocean near Ascension Island. This asteroid’s 100 megaton explosion and its position equidistant between the continents of South America and Africa, ensured absolute destruction across most of the southern hemisphere within 48 hours.

In between the two asteroid strikes, and recognising that humanity was close to extinction, those countries who had nuclear warhead capacity decided to settle long outstanding grudges, and launched a torrent of warheads across both Hemispheres.

North Korea tried to attack its despised southern neighbour, but six of its fifteen warheads detonated on take-off, destroying itself. China saw the Korean launches and enabled its doomsday sequence against all of its traditional enemies, which obliterated most of western Asia, along with areas in Europe and North America.

Pakistan and India eliminated each other’s presence along with most of the Middle East, and Israel completed that undertaking with missile attacks against long-standing regional enemies.

Any human presence left on the North American and Asian continents including America, China and Russia soon evaporated under the blitz of hundreds of missiles. By the time 24 hours had passed since the first asteroid strike, it was estimated no human life was capable of existing on either continent.

Parts of Europe were the final survivor, despite France and the United Kingdom eradicating each other over some long-forgotten hostility. The rest of its citizens struggled on for several days until nuclear winter blanketed the continent and stopped the sun from shining. The human race finally achieved Mutually Assured Destruction.

Within 12 months, there were no living organisms on the planet. The last humans alive had been on the space station with its grandstand view of the planet’s destruction. Self-annihilation took the form of a consented destruction of the slowly orbiting platform, after it was agreed there was no future for the astronauts.

Non-sentient AI Droids had been travelling the earth for almost a decade before those eight days – a result of a winning entry in the Earthshot prize started in 2020, by Sir David Attenborough and Prince William. The concept was simple: gather examples of every living plant from the smallest bacteria, to the most extensive and extraordinary organisms, such as the giant Sequoia tree. The given definition of organisms included algae, fungi, lichens, mosses, ferns, conifers and flowering plants.

They were to be gathered by the droids and returned to biodomes constructed on every continent, so that they could be catalogued and preserved before extinction events removed them from the planet. The construction of these collectors allowed for travel overland or through water, and a small contingent could fly – enabling access to the remotest parts of the earth. The advanced technology of batteries meant that the droids could function continuously in their role for many decades.

2032 ended the experiment. It obliterated the biodomes and destroyed the collections. Earth now consisted of wastelands metres deep in the ash, which settled after the cataclysmic events.

The majority of the droids had been destroyed alongside the ungrateful previous inhabitants of the planet. One survived and continued to traverse the unnamed regions uncompromisingly – obeying its programming to find life.

Designated as a flying unit, it travelled mainly across the region previously known as Antarctica, which now was a series of small ice-floes moving across ash-covered seas. Scanning and then travelling to each landmass, it diligently performed its allocated function. Despite its AI functionality, it had no emotional capability, nor any concept of its role. It did not comprehend the futility of its purpose, or understand that the project no longer existed.

Constructs such as night and day didn’t exist for the Droid, assigned as ES-517/r when assembled. Earth’s atmosphere was polluted to such an extent it could never be determined what the difference between the two time periods was anyway.

Every minute of every day ES-517/r searched a pre-determined grid, directed by satellites that were executing the functionality programmed by long-dead fingers. Its sensors and receptors analysed the surrounding landscape, searching for the reason it existed.

Landing on a large landmass, it resumed its function; utilising advanced sensors to scan the surrounding areas. It detected nothing. This was the same outcome as the unmeasurable periods previously, since contact with any human had been lost.

As its systems were refreshed to begin flying to the next floe to continue the pointless task, it detected traces of a variation potential (VP). These were one of the electrical responses programmed as a method of tracking life.

Plant cells are not neurons, but they can be electrically excitable and display rapid electrical responses in the form of VPs to environmental stimuli. These electrophysiological signals are detectable by sensors tuned to identify the emitted charged ions.

ES-517/r moved to the identified area and became motionless by what appeared to be the top of a rocky outlet, pushing through the surrounding ash. The Droid had no requirement for visual input. However, its creators had mounted highly tuned lenses, so that images of discoveries could be transmitted and recorded before the droids reached their assigned biodomes. If humans had been capable of viewing the file images sent from ES-517/r, they would see a grey ash-covered plant stem rising from the rocks. There were minimal leaf nodes on the stem, each of them bare, but close to the end of the stalk after the final internode, was a petiole with a solitary leaf attached.

Adjusting the machine learning of its original programming, ES-517/r gently extended the mechanical arms it was equipped with and reached towards the plant. Gentle streams of compressed air flowed from a tip on one of the components – delicately removing the dust covering the vegetation. After some time, the plant was free of the dirt and dust, and the cameras could identify a single green leaf attached to the stem.

Searching the databases located eight hundred kilometres overhead, ES-517/r queried what the next movements were that it should follow. Receiving no response as no human was alive to provide the required sequences, the Droid could only follow fallback procedures and remain in standby mode waiting for further responses which would never come.

Many hours later, the last green leaf shed silently from the stem falling gently to the barren ground. The protective layer had been removed from it, causing its ultimate decline in the poisonous atmosphere.

ES-517/r woke from its standby state when it no longer detected any electrophysiological signal from the plant. Directing its camera towards the decaying leaf lying on the ground, it filed the encounter in the databanks, and moved silently away to continue its futile search.