On April 15, 2014 I hosted my second Reddit – Ask Me Anything Session. The response from the Reddit community was great and many insightful questions were asked. Here are the top-10 questions from this event:
#1 – I have trouble planning my weekend more than a day in advance. What are some of the hassles of trying to plan a scientific mission that won’t be completed for another decade?
In the early days, the biggest hassle was getting the energy to write yet another proposal after being rejected by NASA. Now that we are selected, I have host of daily hassles dealing with government funding (the government shutdown last year really caused some headaches), personnel management, late suppliers, and maintaining our team culture. Our long development timeline also poses a challenge in public relations. We think our mission is great, but most media outlets won’t be interested until the day we are on the launch pad. We are constantly coming up with ways to engage with the public and make them aware of the excitement of working on a spacecraft mission. This AMA is one way that we hope to connect with the community and make them feel part of the team! Thanks for your question.
#2 – Has it been proven by isotope analysis or any other means that the earth’s oceans came from comets?
Great question! This is still one of the outstanding issues in planetary science. The first isotopic analysis of a cometary coma was performed during a flyby of comet Halley by the Giotto spacecraft. These data suggest that the deuterium (heavy hydrogen)-to-hydrogen ratio (D/H) of the comet is much larger than that of the Earth’s oceans, by roughly a factor of two. Subsequent measurements of D/H ratios in comet Hale-Bopp and Hyakutake using radio astronomy appeared to support this result. The D/H ratio of the Earth seemed more consistent with the water found in carbonaceous asteroids – which is usually locked up in clay minerals. Recently the Herschel Space Observatory revealed an ocean-like ratio in the Jupiter-family comet 103P/Hartley 2, reopening the debate. We performed experiments that show that the D/H ratio in the vapor can be very different than in the comet nucleus. So, bottom line, we still have a way to go to determine whether comets or asteroids delivered the water for our oceans.
#3 – How much sample will we collect, what do we hope to find in the asteroid sample and how will we analyze it?
The baseline science requirement is 60 grams (about 2 ounces) of asteroid regolith. However, we also have to be able to measure the amount of sample collected before we stow the sample collector in the return capsule. We measure the moment of inertia of the spacecraft both before and after sample acquisition. It turns out that this technique has a measurement uncertainty of 90 grams (3-sigma). Therefore, our sample collector (TAGSAM) is required to pick up 150 grams of material. Under optimum conditions, TAGSAM can pick up two kilograms of material. We have the capability to attempt sample collection three times. However, we hope to get enough sample on the first attempt. The second two are backup options in case the first attempt does not pick up enough material.
The primary objective of OSIRIS-REx is to return pristine carbonaceous material from the early Solar System. Spectral analysis of Bennu suggests that it is similar on composition to the very rare CI and CM carbonaceous chondrite meteorites. These rocks are rich in organic compounds and water-bearing minerals like clays. We hope to find organic molecules that may have led to the origin of life on Earth and inform the likelihood that life may have originated elsewhere in our solar system. The team’s sample analysis objectives are distributed among five broad categories, based on analytical techniques. These are: mineralogy & petrology, elemental & isotopic composition, organic chemistry, spectral properties, and thermal properties. We use a wide variety of techniques including NanoSIMS, transmission electron microscopy, electron microprobe analysis, mass spectroscopy, gas and liquid chromatography, synchrotron particle accelerators, thermal conductivity analyzers, and laboratory spectrometers.
#4 – Do new chemicals form in the asteroid belt like they do on planets?
Asteroids contain a wide range of minerals and chemicals. Many of these are similar to those found on planets such as silicates and oxides. However, the interiors of some asteroids are chemically distinct from the planets and many minerals are found only in meteorites (fragments of asteroids that land on Earth). In addition, carbonaceous asteroids contain a wide range of organic molecules such as amino acids. These minerals and chemicals formed very early in the history of our solar system – either through condensation in the protoplanetary disk or during geologic processing in the asteroid interior. Today most asteroids are cold and inert. On occasion, two asteroids will collide in a violent collision – providing energy for chemical reactions and creating new minerals and compounds.
#5 – What potential complications might the robot encounter on an asteroid?
Our biggest concern is focused on how the asteroid will respond during the sampling event. We will perform a slow-motion (10 cm/s) touch-and-go maneuver to grab a sample of Bennu. We will then open a bottle of high-pressure nitrogen gas to agitate the regolith and collect it in a large air filter. We worry about sending too much material up towards the spacecraft, potentially coating our optical surfaces with dust and damaging important components. We have learned that in order to model this process we will have to invent some new physics to describe an expanding gas in a micro-gravity environment interacting with regolith grains. Our results to date suggest that all the equipment necessary for the return journey home is safe. We may add a protective cover to one of the lidar (laser ranging) instruments to protect it from damage – in case a second attempt is needed.
#6 – Why is this research and experiment important? (I am all for it, just curious)
OSIRIS-REx seeks answers to the questions that are central to the human experience – where did we come from? and what is our destiny? We are going to Bennu, a carbonaceous asteroid that records the earliest history of our solar system. We hope it contains the molecular precursors to the origin of life and the origin of our oceans. Bennu is also one of the most potentially hazardous asteroids, with a relatively high probability of impacting the Earth late in the 22nd century. It is important for us to study this object to determine its physical and chemical properties, in case an impact mitigation mission needs to be planned in the future. Finally, asteroids like Bennu represent natural resources of near-Earth space, in the form of water, organics, and precious metals. There is potential for substantial economic development in follow-on exploration of these objects.
#7 – What do I think about asteroid mining?
Water and organics are useful for life support and rocket fuel and therefore would support a space-faring economy. The current business model for asteroid mining relies on a steady customer base for these resources in space. Such a venture may be feasible if international interest in space exploration continues to increase. Another angle on asteroid mining is to extract precious metals like platinum and return them to Earth. I calculate that a 10-meter asteroid is worth ~$10-million, with $9M in iron, nickel, and cobalt and $1M worth of platinum. Given that OSIRIS-REx costs $1-billion, we have long way to go before this business plan closes. What we really need to do is bring down the cost of accessing space.
#8 – What are the chances of finding a harmful bacteria/virus in the sample?
We consider this to be a very low probability event. We don’t expect any microorganisms on Bennu. It is too small and the radiation doses would kill anything living on the asteroid in a very short time. We had to prove this as part of our Planetary Protection rating – which is Unrestricted Earth Return – meaning that we do not have to take any special precautions to avoid contaminating the Earth with extraterrestrial life. Instead, we hope to find organic molecules that may have led to the origin of life on Earth. We will focus on measuring the organic molecular inventory of the samples but don’t have any plans for biological assays. We will keep the sample under nitrogen purge to avoid contaminating it with terrestrial microbes.
#9 – How do I get a job in planetary science or working on a spacecraft mission?
I describe my initial steps in my Journey to the Asteroid Frontier – Part 1 in one of my blog posts with a follow on in Part 2. I was introduced to planetary science as an undergraduate at the University of Arizona when I received a NASA Undergraduate Research Space Grant to work on the Search for Extraterrestrial Intelligence. The idea of communicating with an alien civilization across the vast expanse of space inspired me to pursue a career in planetary science. I focus on the formation of planets and the origin of life to understand the likelihood of alien life arising and evolving elsewhere in our universe.
As for young people wanting to get into this line of work – study hard and do well in school. Graduate high school and go to college. Find people with similar interests. Start with the basics – math and physics, then work your way up from there. Planetary science is multidisciplinary and requires knowledge of math, physics, chemistry, geology, biology, etc. Once in college, he should try to get a job in a research lab. Talk to scientists and engineers that are working on projects that interest and find ways to volunteer in their labs. Undergraduate research opportunities are key to getting needed experience for a job in the aerospace industry or for getting into a good graduate school. Be persistent, arrange for tours of local labs, and make it clear that you are interested and motivated to pursue a career in this field. Once you get the job, do it well and show initiative to move up to more responsibility.
I am optimistic about the future of space exploration for several reasons. First, despite budget cuts in recent years, the United States has a great space program with many exciting missions in the future including Mars 2020, the Europa Clipper, and, of course, OSIRIS-REx. In addition, other national space agencies are ramping up their programs including India, China, Russia, and the Europeans. Finally, I think we are starting to see some serious interest from industry in commercial development of space. If these companies take off then planetary scientists will be in high demand.
#10 – What powers and propels OSIRIS-REx towards Bennu and how fast does it travel?
We have two solar arrays to provide power to the spacecraft. We have two Li-ion batteries to store power for periods when we are not in direct sunlight (such as during launch and sampling). The guidance system includes many components including star trackers, sun sensors, a laser range-finder, and on-board image processing capabilities.
I describe the journey to Bennu, including details on the speeds involved in my blog post How to Get to Bennu and Back. We will leave Earth with a hyperbolic escape velocity of 5.4 km/s (over 12,000 mph) on an Atlas V rocket. We will sneak up on Bennu with a relative approach velocity of 20 cm/s (~0.45 mph). When we return to Earth the sample return capsule will hit the top of the atmosphere with a speed of 12.4 km/s (27,738 mph).