Solar system exploration Q&A with Cullen Blake

A Q&A with Cullen Blake of the School of Arts and Sciences offers insights on recent astronomy news headlines and on the future of solar system exploration.

a satellite flying above earth with the moon in the distant background

It’s only the second week of the New Year, but 2019 has already been a busy one for the field of astronomy. From the New Horizons spacecraft charting the most distant flyby in space exploration history to China landing on the far side of the moon, astronomers are already making headway towards a busy and productive year of studying the solar system.  

Cullen Blake, an assistant professor in the Department of Physics & Astronomy, is an observational astronomer at Penn. He specializes in the search for exoplanets, which orbit stars outside of Earth’s solar system. His work focuses on developing the hardware and instrumentation required to make these discoveries. 

Penn Today sat down with Blake to discuss the busy start of 2019 in the context of the research of solar system exploration. Blake also highlights what astronomers hope to learn and explore in the coming years.

What’s so appealing about the far side of the moon? 

The far side of the moon isn’t really unique; we just call it the far side or the “dark” side because we don’t see it here on Earth. This is because the moon has a special way that it orbits Earth: the period of spin on its axis is the same as the amount of time that it takes to orbit around Earth. 

There’s a lot you can do from a scientific perspective on the far side of the moon. Since you’re facing away from the sun, you can make clearer observations of the sky. And because the moon has no atmosphere, you can use things like X-ray telescopes to study the cosmos. X-rays are blocked by Earth’s atmosphere, and our atmosphere also blocks some radio waves as well. So going to the far side of the Moon allows us to make astronomical observations that we can’t make on Earth. 


lunar rover driving down a ramp onto the moon
China's new lunar rover, known as Yutu-2, photographed by the Chang’e-4 probe as it takes its first “steps” on the far side of the moon (Credit: CNSA)


In addition to being a better place for X-ray and radio telescopes, what else can we learn from going to the moon?  

 Missions to the moon would let us test new technologies or study how an extreme environment impacts the health of astronauts. This type of mission, where we have people stay for an extended period of time on the moon, would be invaluable for figuring out how one might set up a colony on Mars. 

Do you think NASA will be heading to the moon anytime soon?

The U.S. doesn’t have the ability to send people into space anymore, and it’s been a long time since we sent people to the moon. I would be curious to see what happens if China sends their own astronauts to the moon and whether that motivates Congress to allocate the money to do that mission again. It’s certainly not technologically impossible, just expensive.

A trip to the moon takes a few weeks, but New Horizons has been traveling for more than 10 years. How do scientists prepare for these extremely long-distance journeys?

A lot of the preparation is technical; the components of the spacecraft have to be stable and robust for decades. It also needs a reliable power source that will keep everything going, and it needs to be built so that scientists on Earth can change the course of the spacecraft if they need to. For a mission like New Horizons, there also have to be very specific plans about the science: What the goals are, what data will be collected, and where the spacecraft will go. 

Another thing that scientists have to consider is that the further the spacecraft gets from the sun the harder it is to get data. New Horizons has one antenna that sends images back to Earth. These images are huge, similar in size to what you would get from a digital SLR camera. The challenge is that the bandwidth from way out there is slower than a dial-up modem. It works at a few hundred bits per second, compared to the first-generation modems that were closer to 28,000 bits per second.

It takes a long time to get the data, so scientists have to be careful about what they take images of. It will take around 20 months to get back the images that New Horizons has taken just in the past few days. 

What makes New Horizons’ journey such an important one?

One of the really rare things about New Horizons is that the mission was enhanced and extended mid-course. At some point on the way to Pluto, a journey that took more than 10 years, scientists decided that New Horizons could keep traveling in order to visit other objects in the outer solar system. 

These scientists might have had a vague idea of where they would go after Pluto, but specific places to visit within the Kuiper belt would not have been chosen pre-launch. Some of the objects might not have even been discovered when New Horizons was first launched. The one that ended up being chosen [Ultima Thule] was easy to get to and bound to be interesting because of its shape and structure.


map of the solar system showing where probes have traveled
A map of the course taken by New Horizons and other previous solar system probes. After flying by object MU69 (better known as Ultima Thule), New Horizons will eventually complete its journey through the Kuiper Belt and travel towards interstellar space beyond the solar system (Credit: NASA/Johns Hopkins University Applied Physics Laboratory).


What do scientists expect to learn from exploring the Kuiper belt and from Ultima Thule?

Part of what makes the Kuiper belt interesting is that it contains some extremely old objects, what we consider primordial pieces of the solar system. We can find other very old objects in space, but they are usually very small. In contrast, the objects in the Kuiper belt are miles across. 

The theory of how planets form is that smaller pieces of rock get stuck together until they become larger and larger chunks that eventually form the seed of a planet. Ultima Thule is two large chunks of ice and rock, called planetesimals, that are stuck together. We hope that by studying how the two rocks are joined, as well as visiting other primordial rocks in the Kuiper belt, we can gain some insight into how planets are formed. 

What’s on the horizon for astronomy in the coming months and years?

There’s a new NASA mission that recently launched called the Transiting Exoplanet Survey Satellite that will be looking for exoplanets. That program is just starting to release its first data, so I think we are going to see some really interesting results on exoplanets. 

We’ve also been patiently waiting for the James Webb telescope, which is the successor to the Hubble telescope. Hubble has been a great telescope but it is now quite old, and the James Webb will be a lot more capable in many ways. It’s a big ambitious project that’s falling behind schedule, but the hope is that we’ll see some of the technical aspects get sorted out in the next year. 

In the longer-term, the NASA Mars road map is planned out well into the future, and the next Mars missions are currently in the works right now. There’s also a lot of interest in sending probes to the moons of Jupiter. These moons are covered in ice, but the thought is that there might be water below that ice. 

We’ll certainly have an exciting next couple of years in the field of astronomy.