Phoenix Launches to Mars
Peter H. Smith > Principal Investigator


As I write these words, the launch of Phoenix to Mars is less than a week away. By coincidence, August 3, 2007 (the first of a 22 day launch window) will be exactly four years from the date of our NASA selection as the first Scout mission. Four years of hard work validating and testing our spacecraft; building and characterizing its scientific instruments; and preparing for the mission itself.

Choosing the scientific goal for Phoenix was easy. In February 2002, Bill Boynton (University of Arizona) and his team announced that the Gamma Ray Spectrometer aboard the Odyssey orbiter had discovered water ice surrounding the permanent polar caps, both south and north. Nearly 25% of the surface area of Mars poleward of 60° has near surface ice: a permafrost region similar to Siberia or northern Alaska. Landing on this unexplored terrain and investigating the properties of the icy soil seemed a natural and attainable goal for a Scout mission. NASA agreed.

Unlike the Earth, Mars is rather unstable in its orbit and tends to realign its spin axis and de-circularize its orbital path with time periods of approximately 100,000 years. As the polar regions are tilted toward the Sun and the orbital path brings the planet to its perigee, global warming occurs and Mars may actually enter a wet period caused by the melting of the permafrost ice.

Our science team strives to answer the questions: can we find evidence that these wet periods actually occur and does this provide a habitable environment for Martian microbes? We know from recent studies of the Earth that life survives under the most extreme conditions from inside the failed reactor at Chernobyl to hydrothermal vents at the bottom of the ocean. If life has ever existed on Mars could it have evolved to find local niches where conditions are favorable?

Our studies of Mars have proven that life is not easily found on the Martian surface. The atmosphere has only the slightest hint that there may be biologically-produced gas (methane) at the parts per billion level. None of the fleet of orbiters can point to a location where life exists. Without exploring the surface, answers will never be found to this most intriguing question—are we alone?

Our name stems from the deliberate reliance on using existing hardware and development teams that seemed doomed to never achieve their goals. After the loss of two spacecraft in 1999, the 2001 mission was canceled. This was particularly painful since it was well into its assembly and test phase. However, no data was returned from the instruments on Mars Polar Lander and the 2001 lander was placed in a large box waiting for the day that it might be given a new mission.

The Phoenix mission reassembles the pieces and activates the engineers and scientists who had spent as many as ten years of their careers developing these space-qualified systems. As the principal investigator of the mission, I aligned the project with the Jet Propulsion Lab in Pasadena to manage the project and design the mission. The development contract as placed with Lockheed Martin in Denver who had originally built the spacecraft and were guarding the box.

Unfortunately, after more than three years valuable pieces had been scavenged from the spacecraft and, on the start of the project, our first job was to inventory just what we had inherited. A series of heritance reviews attended by system experts examined the documentation and engineering calculations that supported the spacecraft design. Clearly, most of the avionics were in good shape since exact copies of the electronic boards were part and parcel of the Odyssey spacecraft and several other spacecraft.

These reviews led to an extensive series of reliability tests starting with the propulsion system. Hot fire tests validated the design of the spacecraft to withstand the pounding that the powerful thrusters impose on its components. All the twelve subsystems on the spacecraft went through similar scrutiny. Finally, in April 2006 the spacecraft began its final re-assembly and test program. The scientific instruments were installed in the summer of 2006 and by the winter the spacecraft started environmental testing to prove that it could survive the harsh environments of space and the Martian surface.

Since May 7 of this year, the spacecraft has been at the Cape Canaveral facility and is now installed 12 stories up on top of the Delta 2 launch vehicle. Once the fuel in loaded you can feel the power of the Delta straining to break the gravitation bonds of the Earth and start its mission to Mars.

While the launch is complex and dangerous, hundreds of payloads have been placed into orbit and the success rate is exceptionally good. The ability to refine the procedures developed through many tough learning experiences has built our confidence that launch will be a low risk phase of the mission. The same is not true of landing on Mars.

The success rate for landing on Mars is poor. Because of the 15 minute or more time delay and the 6 minute deceleration from the top of the atmosphere to the surface, there can be no real time control of events. Mastering the complex sequence of events through the five phases of descent is the work of a team of experts at JPL and LM. The Phoenix landing cannot be tested in advance of the mission; it is a one-time occurrence with the success of the mission at stake.

We simulate landing with super computers carefully modeling the physics of entry, the wind vectors and the thruster control systems. Thousands of computer runs describe the hazards and consequences as model parameters are randomly adjusted. Naturally, the physical properties of the Martian surface are important too. We must find locations where rocks are widely spaced—there are no airbags to soften the impact. So far we have been able to reduce the inherent risks to an acceptable level, but this does not take into account the unknowable system failures that can occur. Landing is the highest risk phase of the mission and occurs on May 25, 2008.

Our scientific mission begins shortly after landing. For three months, the science team assisted by a well-trained spacecraft team operating from the Science Operations Center at the University of Arizona will image the surface, provide locations for digging up samples, and deliver these samples to instruments on the deck of the spacecraft. Powered by solar energy, we have a short amount of time to conduct our experiments, therefore, every day is valuable and the team lives on Mars time with a 24h 40m day. As Mars transitions from summer to winter our operational time shortens and eventually there is not enough energy to heat the spacecraft and the cold temperatures will kill it.

But those few months are crucial for answering the questions posed at the beginning of this article. We will determine whether the soil above the ice has ever been modified by the presence of liquid water. There are key indicator minerals and evaporates (salts) that are strong indicators that water has been present. The detection of complex organic molecules like proteins and amino acids would provide evidence that we have discovered a habitable zone.

Alas, we do not expect to provide a final answer to the life on Mars question, only whether the ingredients for a habitat exist. Are realistic to expect that landing blindly on one spot on Mars will uncover clear evidence for life?

I don’t think so.

However, the mission is valuable as a stepping stone to inspire future missions to follow in our path and search the northern plains for the actual inhabitants of a zone that we determine is habitable.