In the film The Martian, astronaut Mark Watney faces the challenge of surviving on Mars after being stranded. To ensure his survival, he cultivates potatoes using the Martian soil. The feasibility of growing plants on Mars or the moon is somewhat uncertain, as we have yet to experiment with plant growth on those celestial bodies. However, it is also promising because we have successfully grown plants in space aboard various spacecraft for years. In The Martian, Mark Watney uses creative techniques to grow potatoes, showcasing human ingenuity in overcoming the harsh conditions of extraterrestrial environments.

The International Space Station (ISS) circles Earth and functions as a unique laboratory where astronauts reside and perform scientific experiments. Initially, during the early phases of space exploration, experiments involving plant growth on spacecraft were conducted mainly for research to understand their behaviors and growth patterns in various conditions, including microgravity and limited environments. In recent years, NASA has begun to explore the viability of cultivating plants in space as a sustainable food source for astronauts. Fresh produce offers essential nutrients and dietary variety, contrasting with the dehydrated and pre-packaged meals that predominantly constitute an astronaut's diet. Thus, ensuring a consistent supply of fresh food has been a significant goal for NASA.

Space gardening not only provides health advantages but also psychological support for astronauts. Tending to plants can alleviate stress and enhance their mood. Since plants represent a piece of Earth, their colors and scents introduce some sensory diversity into the sterile environment of space. The International Space Station experiences up to sixteen sunrises and sunsets daily, which can lead to sleep disturbances for astronauts. Engaging in gardening activities may help them to better perceive time's passage, thereby alleviating some of these sleep-related issues.

Although not widely implemented yet, cultivating plants aboard a spacecraft could help diminish carbon dioxide levels, generate oxygen, and even supply drinkable water through the process of transpiration. Such practices might contribute to creating a more livable atmosphere for astronauts. However, several critical questions remain. Firstly, what are the necessary conditions for plant growth, and secondly, how can these conditions be replicated within a spacecraft environment? Essential factors for plant development include water, soil, gravity, and light, all of which are limited in space. Over the years, various experiments have been underway to explore methods for successfully growing plants with minimal access to these vital necessities, aiming to enhance the viability of long-term human habitation in outer space.

On the International Space Station (ISS), water is a limited resource, and its utilization is meticulously managed and recycled whenever possible. Approximately 93% of the water on the ISS is obtained from recycling the air that astronauts exhale, along with their sweat and urine. Similarly, growing plants in space faces challenges due to the impracticality of transporting heavy soil. Furthermore, the absence of gravity causes liquids and soil to float away, complicating the process of sustaining plant life in such an environment.

To support space-based gardening, NASA has created a specialized container known as Veggie, tailored for use on the International Space Station (ISS). This unique system establishes a conducive artificial environment for plants to thrive in zero gravity. It features plant pillows, which are essentially bags filled with soil, nutrients, and fertilizer. Seeds are attached to small wicks that are inserted into these bags to absorb water. At the base of the Veggie, there is a water reservoir that is covered with a permeable fabric, allowing water to flow through. Another similar fabric on the underside of the plant pillow permits water to seep into the soil, facilitating plant growth.

What role does gravity play in plant growth? Traditionally, it was believed that gravity helps roots to develop properly by growing downward and away from the leaves. In a zero-gravity setting, however, roots can grow in any direction since there is no clear up or down. A study conducted in 2010 aboard the International Space Station (ISS) demonstrated that gravity is not essential for typical root development. Although plants may grow at a slower pace in microgravity, they can still direct their growth upwards toward a light source, provided that the light is strong enough and properly oriented.

An essential light source for photosynthesis is necessary for plant growth. While most plants on Earth rely on sunlight, in spacecraft, solar radiation is often unsuitable due to its variable position. Therefore, NASA has implemented the use of LEDs as a lighting alternative. LEDs are energy-efficient and have a longer lifespan compared to traditional lighting options. Moreover, they produce minimal heat, allowing them to be placed closer to plants without risking dehydration or burning, thus promoting healthier growth in confined environments.

Understanding how to cultivate plants in limited spaces benefits not only astronauts craving fresh salads but also has practical implications for agriculture on Earth. Research conducted aboard the International Space Station (ISS) has provided critical insights for farming in regions with scarce water resources, poor soil quality, or restricted space. For instance, vertical farming utilizing artificial lighting has gained popularity in numerous countries. Ongoing studies in extraterrestrial horticulture promise to enhance our knowledge of successful plant growth in extreme conditions. Space gardening offers advantages not only for space travelers but also for Earth's inhabitants, addressing challenges related to climate change and the rising global population.