Why a Return to Earth from Mars Mission is Feasible but Challenging

While the idea of returning to Earth from Mars might seem too complex, it is not impossible. The difficulties are significant, but they are not insurmountable. The key lies in understanding the complexities of leaving Mars and re-entering Earth's atmosphere, as well as the technical challenges involved.

Understanding the Technical Challenges

The main challenge in returning to Earth from Mars is the mass-to-energy ratio required for the spacecraft to escape the planet's surface. Unlike the Moon, which has only 1/6 of Earth's gravity, Mars has a surface gravity of approximately 1/3 that of Earth. This means that the spacecraft must carry a substantial amount of fuel to lift off from Mars, which compels it to carry a large amount of fuel even before it leaves Earth. This factor significantly increases the overall challenge.

According to the mission statistics, it takes about 19 km/s of Δv (change in velocity) to land on Mars, and approximately 9.1 km/s of Δv to return to Earth. In comparison, it takes only 10 km/s of Δv to get to Low Earth Orbit (LEO) and 2.1 km/s to get into Mars Transfer Orbit. The remaining 4.1 km/s is needed to land on Mars. Given that a significant portion of the energy is squandered due to aerodynamic drag, the numbers are still daunting.

Comparing Energy Requirements

It is interesting to note that it takes less energy to get to Mars from Earth orbit (LEO) than it does to get from Florida to LEO. This highlights the complexity of the mission and the sheer amount of fuel required. The mission to Mars involves a total energy expenditure of around 19 km/s, and to return home, it requires about 9.1 km/s of Δv.

Another point to consider is the atmospheric pressure on Mars, which is only 0.00628 atm compared to Earth's 1 atm. A thinner atmosphere makes it easier to escape and allows spacecraft engines to operate more efficiently. However, the challenge lies in re-entering Earth's thick atmosphere, which requires a heat shield and parachutes to handle the high velocities (Mach 30).

Previous Successful Sample Returns

Despite the challenges, humans have managed to return samples from other celestial bodies. The Luna 20, Stardust, and Hayabusa 2 missions successfully returned samples from the Moon and asteroids. However, the NASA Mars Sample Return mission was canceled in 2004, and Russia's Fobos-Grunt sample-return mission to Mars' moon Phobos failed in 2011. While future missions are being planned and sample return missions are certainly possible, none have succeeded to date.

For astronauts, the challenge is even greater. Multiple launches might be required, and rendezvous in Mars orbit or mid-course corrections would be needed. The problems of radiation exposure, food, and power requirements further complicate the mission. However, with enough rockets and funds, it is feasible to send astronauts back to Earth.

While it may be close to impossible within the current technological and financial constraints, the possibility of a human return from Mars remains a tantalizing prospect. With advancements in space technology, it is conceivable that such a mission could be achieved within our lifetimes.

In summary, while the return to Earth from Mars is challenging, it is not impossible. The key lies in extensive planning, advanced technology, and a significant commitment of resources. Future missions could pave the way for the eventual return of human beings to Earth from Mars.