Scott Hubbard (Lexington, Kentucky, USA, 1948) was nicknamed "the czar of Mars" because he was the first director of NASA's Mars exploration program, but focusing solely on his Martian contributions would be selling him short. This veteran astrophysicist, former director of NASA's Ames Research Center, and founder of the Astrobiology Institute of the US agency, has been a key player and witness to the last half-century of space exploration. At 76, his curiosity about the cosmos remains undiminished, as he demonstrated on La Palma Island during the science and music festival Starmus.
A festival where he felt right at home, as he describes himself as a "rocket scientist and musician." He was a guitarist in a band in the 90s and, although he believed that humanity would benefit more from his contributions as a space scientist than as a musician, he still plays music as a hobby.
During his two decades at NASA (between 1987 and 2007), he also served on the committee that investigated the 2003 Columbia shuttle accident.
Founder of the New Space magazine and the Center for Excellence in Private Space Transportation at Stanford University, he actively promoted the involvement of private companies in the space sector. Between 2012 and 2021, he led the SpaceX Crew Flight Safety Advisory Panel, although his first meetings with Elon Musk date back to 2001.
Question. How do you assess the progress of private companies like SpaceX, Blue Origin, Axiom, or Virgin Galactic, and the current state of the aerospace sector, with fully private missions and others in collaboration with the US Government?
Answer. It was something that was bound to happen and, for me, inevitable. In the beginning, only the Soviet Union and the US were involved in space exploration, with intense competition between the two countries. Over time, what I call the business ecosystem has developed, and companies are now carrying out many activities that were previously governmental. Getting into this business is a significant step. Elon once told me, "It's much easier to write computer code than to launch a rocket." There's a reason they call it rocket science; it's very challenging. But it was necessary because the cost of sending a kilogram into Earth's orbit was very high, and only by introducing what commercial companies do very well, which is a production line, can we reduce costs to the point where we can now start using space as a commercial enterprise. However, it's important to remember that companies are not the government, and the government is not a company. They have different incentives and legal structures.
Q. For example?
A. Every time I've asked someone at SpaceX what they do, they respond, "We are a transportation company," which means they have chosen a niche. They are focusing on mass production and reusability, as they recover the first stage of the launcher, which helps reduce the cost of a launch and turn it into a business. The government, on the other hand, should be at the frontier, investing in things that are not commercially viable.I am often asked if Elon will reach Mars before NASA. I say, 'only if he is willing to risk someone's life.' Because SpaceX is a transportation company. If they want to send people to Mars, they have to keep them alive. That means advanced life support, spacesuits, habitats, modules... SpaceX is not building them. A collaboration between the government and the industry is needed to develop these advanced technologies.
Q. SpaceX is testing its Starship spacecraft, with which Musk aims to send an unmanned spacecraft to Mars in two years, and a manned spacecraft before the end of the decade. The last two tests ended in explosions. Do you consider it possible to send one of these spacecraft to Mars so soon?
A. I doubt it. I'll be very direct with you. If your only goal is to send something to crash on Mars, then yes, you probably can. Remember, he sent his own Tesla Roadster into space with a mannequin named Starman on board, which is in an orbit that crosses Mars'. But if you really want to enter Mars' atmosphere, descend, and land on its surface, it's very difficult to do. I haven't seen any evidence that SpaceX, Blue Origin, or any other company can do it. At this moment, only NASA and the Chinese have that capability, as they have successfully landed on Mars once. Our robotic vehicle, Spirit, lasted seven years, Opportunity 14 years, while the Chinese rover lasted a month.
Q. In theory, NASA designed the twin robots Spirit and Opportunity to last three months.
A. That's right. The engineers kept a small extra reserve in their back pocket.
Q. But from the planned three months to the 14 years that Opportunity survived on Mars, there is a significant difference.
A. Do you know why? I set the criteria.
Q. As the first director of the NASA Mars program.
A. Yes, I chose that mission. Mars has a lot of dust, so we thought it would cover the solar panels and the mission would end due to lack of power, as the rovers couldn't recharge the batteries. But it was the only time in my long career that nature helped me. Dust devils cleaned the solar panels. So, this, combined with some engineering, allowed them to last a long time. Ultimately, the Opportunity mission ended when there was a global dust storm.
Q. Veteran astronauts like Valentina Tereshkova or Buzz Aldrin have advocated for a one-way trip to Mars, given the difficulty of the return trip and how expensive it would be. NASA has always talked about a round trip mission, but now with companies like SpaceX, there would likely be volunteers willing to die on Mars. Do you see a one-way mission as possible?
A. Right now, I don't see it. I think if you want people to arrive in good shape, live on Mars, and be able to do something there, you have to take care of their health and performance. They will be in deep space, confined in a small spacecraft for seven months, as the minimum time it takes to reach Mars with current vehicles is six months. We know very little about the effects on human health and performance of such a long journey exposed to microgravity, radiation, and confinement. Now, if something happens or breaks on the International Space Station (ISS), the astronauts turn on the transmitter and say 'Houston, we have a problem.' On the ground, there is a group of 30 to 80 people to analyze the problem and help solve it. But during a trip to Mars, they will be alone and will have to manage on their own. And when they arrive, their muscles will have weakened. On the Martian surface, they will be living with a gravity of 3/8 [about 38% of Earth's], and no one knows what happens to the human body in such an environment. We only have a few weeks of experience on the Moon.
Q. How long will the astronauts going to Mars have to stay?
A. There are two competing architectures. One foresees a 30-day stay on Mars, and the other, 300 days. I spent much of my career in the aerospace industry and over 20 years at NASA, and I don't believe NASA will ever send someone on a one-way trip. Projects like Mars One, which I think went bankrupt, promised a one-way trip to Mars. In my opinion, all of this was just talk, a sales strategy, not reality. I think it would be completely irresponsible to hire someone for a one-way trip to Mars. In his 1961 speech, Kennedy said, "By the end of this decade, we will send a man to the Moon and bring him back safely." So, I don't think NASA will organize a one-way mission; the debate is whether they will stay for 30 days or 300. And if you are going to stay there, where does your food come from? You have to bring it in advance.
Q. So, they will have to send ships with supplies to Mars before the astronauts arrive.
A. That's right. If I were to be the Mars czar again, that is, the director of the Martian program, I would say, 'Let's send resources in advance,' as the Arctic explorers did. They prepared food reserves, but no one knows how to preserve food perfectly for such a long time, at least the good kind.
Q. In his inauguration speech as president, Donald Trump set reaching Mars as a US goal. It was already a goal before, but passing through the Moon first. Do you think the Artemis lunar program will be maintained?
A. I only know what I heard in the testimony of Jared Isaacman, nominated as the new NASA administrator. He has committed to continuing the Artemis program to return to the Moon. Suddenly shifting from a more or less well-planned architecture to sending everything to Mars, I think would delay the program because we are not ready to send humans there. Robots, yes, we have done it, and they are doing well. But sending people is very different.
Q. Based on your experience, would you say it is more convenient to return to the Moon before going to Mars?
A. Yes. Especially to learn how to operate in a reduced gravity environment for a longer period. I didn't think that way before, I was very skeptical, and I believed that if we pushed hard to go to the Moon, we would get stuck there. But now I think we know so little about the human in these environments that we first need to go to the Moon.
Q. So, you have changed your mind on this topic.
A. Yes, analyzing the facts.
Q. During your career, you have worked with several directors of NASA. Do you think that the entrepreneur and private astronaut Jared Isaacman is a good candidate to lead it?
A. Considering everything that is happening, and the chaos of Trump and his administration, I think Isaacman is a good choice. However, in my opinion, he needs a deputy director who understands NASA and the budget process. Jared is an entrepreneur, but he has piloted high-performance aircraft and has traveled to space twice on the private missions of SpaceX Polaris Dawn and Inspiration4, so he has great knowledge. What I don't know is his stance on science; I hope he also supports a good budget.
Q. The Trump administration has proposed cutting NASA's budget for the scientific missions department by almost half in 2026, which would end important robotic missions, such as Mars Sample Return to bring samples from Mars to Earth, which I understand is considered very important.
A. It is, it is a very important mission, and it will be done in collaboration with the European Space Agency (ESA).
Q. Your colleagues are very concerned about this budget cut proposal for NASA.
A. I am also very concerned. We will see what finally happens because the budget approval process in the US is long and complex, and we are not even halfway through the process yet. The other issue is that historically, NASA has been very bipartisan. Democrats and Republicans have always agreed that NASA is good for many reasons: the economy, innovation, education, science, technology (STEM). So I think there are many possibilities that the budget will be quite different once Congress finishes its work.
Q. You were part of the Committee that investigated the Columbia shuttle accident in 2003, in which seven astronauts died. I suppose it was very tough for you. How did that accident change safety measures at NASA?
A. Well, we, the committee members, hoped that NASA would reintroduce a safety culture.
Q. Do you think there wasn't one when the accident happened?
A. Well, in 1986, another shuttle accident, the Challenger, occurred. And NASA, as a result of the Rogers Commission that investigated it, implemented many safety checks. They rebuilt the organization, but over time, the power of that organization diminished. To change a culture, you need leadership from the top for a long period of time. It's not enough to change the organizational chart. So when the Columbia accident happened, and our board analyzed what had happened, we saw some of the same things that had occurred in the Challenger accident. We hoped that NASA had created a permanent safety culture. There were many other technical issues, but this was one of the major conclusions.
Q. One of the participants in the Starmus festival was Michel Mayor, who, in 1995, along with Didier Queloz, discovered the first exoplanet or world outside the Solar System. In April, a team announced that they had found possible signs of life on the exoplanet K2-18b, as they confirmed finding a gas called dimethyl sulfide (DMS), which on Earth is produced by living beings, although it can also be created without the presence of living beings. What do you think about the possibility of life on that exoplanet?
A. Each piece of data adds to the mosaic. It takes more than one observation to convince a scientist that life has indeed been found, but it tells us that there is chemical activity on these planets. One of the people from the NASA Ames center, my former center, designed the Kepler mission, which has allowed us to find thousands of planets in the so-called habitable zone of their star, so at least now we know more about where to look. The field of exoplanets is growing a lot because at the beginning of my career, if I had been asked if there were planets around other stars, I would have said, 'Well, it is expected to be so, but we haven't seen them yet.' And now we are in a similar situation. Many astrobiologists believe that life in the universe is common, but to prove it, you need to detect complex hydrocarbons, a certain amount of oxygen, certain amounts of other chemical elements, etc. My interest is to find out if life ever emerged on Mars, and that's why the Mars Sample Return mission to bring samples to Earth is so important. Because now the Perseverance rover is going to the most interesting sites to collect those samples.
Q. Recently, the Curiosity rover announced the discovery of the most complex molecules found on Mars so far, dating back 3.7 billion years.
A. Mars is smaller than Earth, so it cooled down more quickly. And once that happened, it started to lose its atmosphere and so on. But there was a period, between 4.5 billion years and 3 billion years ago, during which it probably had abundant liquid water on the surface. So you have that, organic compounds, energy, sunlight... the perfect combination to create life.
Q. Besides evidence of past life, could there currently be some form of life on Mars?
A. Yes, I think it's possible. It would probably be microscopic life. The Mars Express and Mars Odyssey probes have made radar measurements suggesting that there is very salty water about a kilometer deep below the Martian surface. And we know that on Earth, there are organisms that thrive in very salty water.
Q. Like in Río Tinto, in the province of Huelva, where there are organisms living in extreme conditions.
A. Yes, I have been to Río Tinto, my friend Juan Pérez Mercader took me there, and he is now at Harvard. It is a very famous place to study extremophile organisms. So yes, I believe it is possible that there are live microbes on Mars today, in very deep areas where there is liquid water. And now that we have those radar measurements, it is more likely to be the case.