Joseph (Joe) Masiero

Associate Research Scientist


This profile series introduces current Caltech/IPAC scientists who support various projects at IPAC while conducting their own research.

In this profile, we feature Joseph (Joe) Masiero, a mid-career associate research scientist at IPAC who works for the Near-Earth Object (NEO) Surveyor Survey Data Center at IPAC. NEO Surveyor will discover and characterize most of the potentially hazardous asteroids that are near Earth after it has been launched (currently expected in September 2027).

Joe is an expert on studies of the composition and origin of the near-Earth asteroid population. Joe tells us how he became interested in science, what his career path leading to the current job at IPAC was, and what he really wants to accomplish during his career. Joe also owns an extensive collection of asteroid remnants he has bought on eBay.

What is your current job title and what do you do in your job (briefly, both functionally and research-wise)?

My title at IPAC is Solar System Scientist, as well as Deputy Principal Investigator (PI) for the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission. My roles include leading the development of the Moving Object Detection Pipeline for the NEO Surveyor Science Data Center at IPAC, and overall mission leadership for NEOWISE. My research focuses on the origins and evolution of the small bodies of the solar system, in particular, the compositional properties of near-Earth and Main Belt asteroids as told by photometry, polarimetry, and thermal modeling. By tracing the near-Earth asteroids to the Main Belt, one can start to understand the collisions that take place in the Main Belt, and the porosity of the Main Belt objects.

Prior to WISE and NEOWISE, we knew the orbits of half a million or so asteroids around the Sun, and we knew roughly what their brightness was. We had no knowledge of their physical properties, though. The Wide-field Infrared Survey Explorer (WISE) started out as an astrophysics mission to create a single map of the whole sky in mid-infrared wavelengths. In seven months of cryogenic operations, WISE was able to observe about a quarter of the known asteroids and give them all diameters and albedos (a measurement of reflected light). WISE also helped us to understand the gas production rate evolution as comets approach the Sun. NEOWISE was an add-on to study the Solar System, specifically to survey the asteroids. We have now surveyed more than 3,000 near-Earth asteroids (or 10% of the known population) with NEOWISE. NEOWISE data have also enabled the discovery of the first known Earth Trojan asteroid. Shown in the figure below is a map of the orbits of Main Belt asteroids showing the compositional trends that were revealed by NEOWISE, which was one of the main results of the survey.

MBA AI Color Bar

This figure shows the orbital semimajor axis compared to the orbital inclination of the asteroids of the Main Belt. The color of each point indicates its geometric albedo (surface reflectivity) as determined by NEOWISE. The clumping structure is caused by families that were formed from catastrophic collisions between asteroids, while the general trend in albedo through the Belt is a feature that traces the different compositional histories these bodies experienced, particularly the water content included when the asteroids formed.

The idea for NEO Surveyor was to design an optimized system for detecting asteroids that will be better than WISEwhich was already very sensitive and gave us a sense of what is the population of near-Earth objects larger than a kilometer. We wanted to answer questions we have about the population of potentially hazardous: how many are out there? What are their orbits? Are there any that could impact the Earth? We also aimed to put statistical constraints on the smaller end of this population. NEO Surveyor will be passively cooled and will have to be farther away from Earth to avoid being heated. NEO Surveyor is going to the SunEarth Lagrange 1 (L1) point, about four lunar distances away from Earth.

How and when did you become interested in science?

I've been interested in science as far back as I can remember. Even in elementary school I said I wanted to be an astronomer. As a four-year old, my father showed me Halley's Comet through his telescope, and that may have provided the initial impetus for my fascination with science and astronomy. My father was an engineer, but he was fascinated by space science and astronomy, so he was very supportive of my pursuit of science.

I also love sci-fi, starting with the Star Trek TV series and movies. Some of my favorite sci-fi authors include Paolo Bacigalupi, James S. A. Corey (Expanse series) and Alastair Reynolds. My favorite sci-fi movies are “Ex Machina” and “Arrival.” I also like cli-fi (climate fiction).

Describe your career path leading up to your current job at IPAC?

After high school, I went to Penn State and majored in astronomy and astrophysics. I also participated in undergraduate research for nearly my entire undergrad career, leading up to an Honor's thesis on quasar absorption lines. I chose this topic as I thought I would get along best with the advisor who was leading this team. However, I learned that the topic, while interesting, was not my passion. I then went to grad school at the Institute for Astronomy at the University of Hawaii, and thought solar system astronomy could be something that I am really interested in. It was a good guess. Again, I picked the advisor based on who I thought I would get along with best. My thesis focused on the rotation and polarization properties of asteroids. I got to observe a lot with the University of Hawai’i's 88-inch telescope on Mauna Kea, and I got to use the CanadaFranceHawaii (CFHT) and Subaru telescopes as well. I even made one trip to the Cerro Tololo Inter-American Observatory (CTIO) in Chile to test an instrument. Unfortunately, we were never able to perform the test, as the telescope broke down just before our time was about to begin.

Immediately after defending my dissertation in 2009, I began a postdoc position at JPL working on analysis of asteroid data from the WISE mission, which launched just two months after I began my postdoc. My Ph.D. dissertation supervisor had run into Amy Mainzer (PI of the NEOWISE mission) and I got in contact with Amy. She told me I could start my postdoc with her the day after I finished my Ph.D. Because IPAC hosted the WISE Science Data Center, we spent a lot of time in Morrisroe (building where most of IPAC is located) during the prelaunch and operations period, so I had a visitor's office at IPAC from the beginning of my postdoc at JPL.

I had joined the NEO Surveyor team in 2010 when it was the NEOCam proposal. I joined JPL as a staff scientist in 2012, helped write the proposal to reactivate NEOWISE in 2013, and became the Deputy PI of NEOWISE in 2017. The NEO Surveyor team at IPAC needed someone with NEO Surveyor experience, specifically someone with moving object pipeline expertise, and I moved to the friendly confines of IPAC in 2020. I very much enjoy working with people at IPAC, and the atmosphere here is very collaborative and relaxed.

What do you dream of still achieving, either in your science career or otherwise?

There are many contradictory theories for the early evolution of the solar system and the origins of the various kinds of asteroids, including the possibility there are objects from beyond Neptune implanted in the Main Belt, and that others of these objects might have been the first solids to form. I hope that through a careful census of the physical properties of the asteroids we can come up with a specific timeline of how, when, and where the different kinds of asteroids formed. For example, the near-Earth asteroid population is not monolithic, but consists of asteroids that are on fairly stable orbits (the bigger ones) and of asteroids on unstable orbits. A lot of these smaller unstable-orbit asteroids have been recently ejected from the Main Belt resonances with Jupiter, and many of the bigger near-Earth asteroids are slowly drifting in from the inner edge of the Main asteroid Belt. Some of the near-Earth asteroids are also dead comets.

Scientifically, I also find extrasolar comets, such as Oumuamua and Borisov, fascinating. These do not really form a hazard to Earth. The Vera C. Rubin Telescope is going to be a game changer in detecting such objects, although NEO Surveyor will be able to detect them as well. Where are they coming from? Their origins are entirely speculative, currently.

What is your best memory related to your science career?

My best memory would have to be when we ejected the cover from WISE and got to see the very first data from the telescope.  It was New Year's Eve, and the whole science team was hunkered down at IPAC flipping through these very first images.  Right away, we were able to see asteroids moving against the backgroundthey were amazingly bright in the infrared images.  That's when I knew WISE was going to change our understanding of the solar system.  It was exciting times, trying to figure out what these brand-new data were telling us.

Tell us about your experience in science outreach. For example, what do you want to be the "takeaway message" for people you talk to at outreach events?

I love doing outreach events and talking to the public.  Audiences generally are interested in learning about hazardous asteroids, how our solar system formed, and where Earth came from.  My main takeaway message is generally: "Yes, there are hazardous asteroids out there, but you, the taxpayer, have hired an amazing team of experts whose job it is to worry about these for you, so you can sleep well."

I also get asked a lot about whether there are Martians or aliens out there. My answer is always "Given how quickly life appeared on Earth, it would be strange if biology and chemistry behaved differently in other places. Bacterial life seems to be a foregone conclusion of chemistry if you have liquid water, a suitable temperature, and carbon in the environment. It is highly unlikely we are the only place where life appeared anywhere. Intelligent life is a harder question, but it seems likely that it would have appeared elsewhere as well. Whether they have visited us is a different matter, as the distances between stars are so incredibly large, making interstellar travel perhaps too challenging. And then there is also the Drake equation (that is used to estimate the number of active, communicative civilizations currently in the Milky Way). Most importantly, we do not know how long civilizations last, an essential input to the Drake equation, making it very hard to estimate whether there are or have been intelligent visitors to Earth."

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