Questions & Answers

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).

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). Carbonaceous asteroids, like Bennu, contain a wide range of organic molecules such as amino acids. These minerals and chemicals formed in the beginning of our solar system – either through condensation in the protoplanetary disk or during geologic processing in the asteroid interior.

The primary objective of OSIRIS-REx is to return pristine carbonaceous material from the early Solar System. This material will provide important clues to the origin of life on Earth and the likelihood that life may have originated elsewhere in our solar system. Our astronomical observations of Bennu suggest that there is abundant fine-grained (<1 cm) material on the surface available for sampling. Our sample collector design relies on loose gravel-like material for collection. Therefore, we expect to find loose, fine grain regolith on the surface of Bennu.

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, you should try to get a job in a research lab. Talk to scientists and engineers who are working on projects that interest you 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.

after Earth return. We do not expect any microorganisms on Bennu and consider finding one a very unlikely event. The asteroid is too small and the radiation doses on its surface would kill any living organism 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.

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.

The Yarkovsky Effect is non-gravitational force which arises when an asteroid receives energy from the sun, absorbs it to heat up the surface, and then re-emits it back into space later in its solar day. This anisotropic emission of thermal radiation imparts a small force on the asteroid that substantially changes its semi-major axis. We will get a much more accurate measurement by tracking the spacecraft in the vicinity of Bennu. In addition, using our thermal emission spectrometer, we will get spatially resolved information on the total amount of radiation emitted from the asteroid surface as a function of the time of day. This information will allow us to test the theory of the Yarkovsky effect and improve our knowledge of the fundamental asteroid properties that give rise to this phenomenon. We can not get such detailed and high-quality information from ground-based telescopic observations.

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.

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.

within the budget provided ($800 million over 14 years of the mission). While a new instrument or component to the mission could further our science knowledge, it always comes at a cost. A new instrument requires management, engineers, scientists, and quality assurance reviews. Our [five instruments and the Touch-and-Go sampler] (instruments page) will capture the historical and compositional makeup of Bennu and retrieve a sample for Earth return. This combination was selected because it can meet all science objectives within the allotted budget.

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.

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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.

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.

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.

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.