In last week’s episode of “MasterChef Junior,” the Top 20 remaining contestants face some space-age challenges. The best home cooks in America between the ages of 8 and 13 battle it out in a Mystery Box cheese challenge, and get a visit from a real-life astronaut.

The kids walk into the “MasterChef” Kitchen and are surprised to find a giant Mystery Box. They find the three judges inside the box, which lifts up like a spaceship. Gordon Ramsay, Graham Elliot and Christina Tosi are all wearing astronaut suits. They tell the group of eager children that NASA astronaut Tracy Dyson is paying them a visit.

Dyson walks in and the kids are mesmerized. Many of them admit that they dream of becoming astronauts one day. She shares about her experiences in the international space station, and even shows off packets of dehydrated food that they take up to space.

Now knowing that the Mystery Box challenge is related to the moon and outer space, the clever kids guess that they have cheese under their boxes. After all, many kids in America are told that the Moon is made of cheese, as they are growing up.

Addison, JJ and Kaitlyn come up with the top three dishes in the cheese challenge. Addison makes a three cheese ravioli using fresh pasta, ricotta, mozzarella and asiago cheese. She tops it with a wonderful basil pesto sauce that impresses Gordon.

JJ comes up with a cheese enchilada filled with sharp cheddar and smoked gouda. The depth of flavor in his sauce is a hit with Christina. The parmesan crisp on top of the enchilada really elevates his dish to MasterChef quality.

Kaitlyn serves up the winning dish of the challenge by veering away from the savory route. She opts to make a dessert and impresses the judges with her ricotta cookies and lemon cream filling. It’s her take on the classic French macaron and it’s enough to give her a major advantage.

Kaitlyn is exempted from the elimination round and is safely through to next week. Before she could go up to the balcony, the judges reveal the star ingredient for the elimination challenge. A large selection of fish rolls out and it is revealed that contestants will be given a selection of whole fish that they can prepare as they please.

Before leaving the kids to fend for themselves, Graham gives them a demonstration on how to fillet a whole fish. He uses a giant moon fish to show off his impressive skills with a knife. Kaitlyn is then given the task of being the fishmonger for the day. She hands out the fish to each of the contestants, who can choose which fish they want to cook with.

After a full hour, the judges call out the best and the worst dishes of the day. Nine-year-old Avery serves an impressive pecan crusted halibut with sweet potato mash and sour sauce. Derek’s dover sole also stands out with his fingerling potatoes. The Asian flavors clearly dominate the evening as Ian, Kaya and Nate all excel using eastern ingredients.

Despite forgetting to season his fish, Ian’s seared yellowfin tuna is saved by his sesame oil dressing. Meanwhile, Kaya’s salmon confit with daikon puree also impresses the judges. However, Nate wins the challenge with the vibrant flavors of his seared yellowfin tuna, paired with cucumber noodles, shiitake mushrooms and green beans.

While some came out on top, others ended up at the bottom of the pile. Jaeclyn’s fish tacos made with Tai Snapper were quite bland. She forgot to taste her fish and didn’t realize that it needed more seasoning. However, she did just enough to stay in the competition.

Vivian and Kyndall end up getting sent home. Vivian’s tai snapper with ratatouille with lemon sauce came with a soggy fish and and raw vegetables. Kyndall, served branzino over rice and a parsnip puree and roasted vegetables. Just like Vivan, her fish was soggy and her vegetables were raw.

Only 18 contestants remain in the running towards becoming the next “MasterChef Junior.” The next episode airs on Friday, Nov. 27, at 8:00 p.m. EST on FOX.