Can the lichens that once transformed the Earth's land be used to transform Mars in the future?

Produced by: Science Popularization China

Author: Liu Liqiong (Institute of Microbiology, Chinese Academy of Sciences)

Producer: China Science Expo

Are lichens plants?

Lichens are so disguised as plants that they have long been hidden from human eyes. When British-Norwegian explorer Carsten Borchgrevink first discovered lichens in Antarctica in 1895, he claimed that they were "green plants." In fact, lichens are a symbiotic organism of fungi and algae (or cyanobacteria), and are essentially fungi.

Habitat of the genus Pseudosphagnum at an altitude of 4500 meters

(Image source: Kunming Institute of Botany, Chinese Academy of Sciences)

Lichens have a variety of strange and artistic appearances, and they are not all "green plants". They are complex organisms that are symbiotically formed by fungi (mostly ascomycetes, a few are basidiomycetes) and algae (mainly green algae) or cyanobacteria . Because fungi and algae or cyanobacteria have been closely combined with each other for a long time, they become a separate fixed organism group with unique morphological, structural, physiological and genetic characteristics.

Habitat of the genus Pseudosphagnum at an altitude of 4500 meters

(Image source: Kunming Institute of Botany, Chinese Academy of Sciences)

Fungi and algae are like brothers, mutually beneficial and cooperative. Algal cells perform photosynthesis or nitrogen fixation to produce organic nutrients for the entire lichen, while hyphae provide a suitable shelter for algae and cyanobacteria, and absorb water and inorganic salts to provide raw materials for their photosynthesis and nitrogen fixation.

However, some people have conducted experiments in which they cultured the fungi and algae in the lichen separately under nutrient-free conditions and found that the algae were almost not affected by starvation, while the fungi starved to death. In other words, it can be considered that the fungi benefited more from this relationship.

Lichens are extraordinary survival artists

The aliens in "The Three-Body Problem" can dehydrate themselves to protect themselves under extremely high temperatures, and then wake up and continue to be alive and well when conditions are right. It may be difficult for humans to cope with such harsh living conditions.

But this is not a problem for lichens. Lichens are water-changing organisms. When natural conditions change, they will quickly start the response mechanism to change the water content in the cells and change physiological reaction processes such as respiration or photosynthesis. High temperatures of 60℃ and extreme cold of -50℃ cannot stop its small footprints moving forward. The wild world is full of the ambition of the little lichens.

Concept map of future living environment

(Photo source: veer photo gallery)

About 8% of the Earth's land surface is covered by lichens, from the equator to the poles, from plains to mountains, in deserts, grasslands, and forests. For example, during the second scientific expedition to the Qinghai-Tibet Plateau, researchers from the Kunming Institute of Botany, Chinese Academy of Sciences, discovered 11 new species of lichens and established the genus Pseudolichen.

The distribution and growth environment of lichens are very wide. Lichens can be seen growing on all kinds of natural substrates such as rocks, soil, trees and mosses. They are widely distributed. Some naughty lichens grow on artificial materials such as cloth, paper, glass, silk, sculptures, paint, wood, iron, etc. They are the true love of archaeologists, and they can make many archaeological discoveries with their help. Some lichens are actually even more naughty, such as growing on bird feathers, and even on living insects and turtles.

Lichens carry the human dream of interstellar migration

Humans have been striving to live longer, and in this regard, lichens can be said to have realized the human dream. Chinese scientists have discovered a fossil suspected to be a lichen in Guizhou Province, and it is estimated that it is 600 million years old. It should be noted that on the 4.6 billion-year timeline of the Earth, higher plants only emerged 430 million years ago.

Tea stain lichen

(Photo courtesy of Yang Qiuxia, Institute of Microbiology, Chinese Academy of Sciences)

Imagine the ancient times, when fungi and algae were pushed by the tides, joyfully landing on the ground from the shallow sea, combining to form lichens, landing on an unknown new world, and then began to transform the land without complaint and tirelessly. They secreted lichen acid, corroding and dissolving rocks; when the lichens died, their remains decayed and mixed with the rock particles they decomposed, returning to eternal silence with time. They finally created nutrient-rich soil and finally gave birth to a world of life where all things shine.

Cladonia

(Photo courtesy of Yang Qiuxia, Institute of Microbiology, Chinese Academy of Sciences)

Since we can “shape” the Earth, can we “shape” other planets?

Scientists think so too.

In 2005 and 2007, they sent different lichens into space twice. After experiencing harsh conditions such as vacuum, weightlessness, drastic temperature changes, and extremely lethal cosmic ray radiation, they finally returned to Earth alive and well, and lived up to everyone's expectations, recovering their vitality and still looking as lively as before departure.

Therefore, lichens may be the most suitable biological group for ecological transformation of Mars or some satellites to make them suitable for higher plants or even human life. Scientists hope to conduct more experiments, such as artificially creating a ground environment similar to the moon and Mars to grow lichens. If successful, humans are expected to transform the atmosphere and soil of alien planets by planting lichens, and then introduce higher plants and animals, rebuild an ecosystem similar to that of the Earth, and establish a thriving "new Earth".

Humanity’s dream of interstellar migration shines brightly on the lichens.

Conclusion

Lichens have quietly shaped the face of the Earth over the long years. When we raise the grand idea of ​​"Can humans create another planet through lichens?" with great anticipation, we have to face the complexity and challenges of reality. This requires us not only to have a deep understanding of the biological characteristics of lichens and their interaction mechanisms with the environment, but also to master advanced aerospace technology, ecological engineering and methods to maintain the stability of the ecosystem in the long term.

More importantly, this idea reminds us to reflect on our relationship with the Earth. While pursuing the stars and the sea, we should cherish and protect our only home. Therefore, using the study of lichens to promote the restoration and protection of the Earth's ecosystem may be a more urgent and significant task.