It had been a rough day. Under instruction to perform X-ray diffraction analysis what JPL was calling "intriguing Martian material" but Curiosity had started thinking of as "damn hard-to-access shiny rocks", she kept being stymied by her inability to get a clean sample core. It seemed pretty clear she'd either break the drill bit or contaminate the sample if she followed her instructions to the letter.
On the other hand, it was a perfect day on Mars. The solitude was a gorgeous, restful weight. Gale Crater felt like coming home after the organized chaos of JPL.
She was glad she got to talk to them back at home, Matt and Vandi and Scott and all; she wouldn't know what to do with herself if they weren't guiding her. But for the most part she was on her own, moving slowly over a landscape she'd been built for. The quiet wrapped around her like a blanket. Even on days like today, she settled back in the science and felt it take care of her.
The only break in her quiet, besides the brief communication bursts with Pasadena, were her conversations with Opportunity. She'd hailed Opportunity not long after landing, before even finishing her post-landing software upgrade. She'd been contemplating for weeks how best to open communication. Casual -- Yo, sis, how's it hanging? Formal -- Greetings, Opportunity. My name is Curiosity and I am your sister. In the end all of her rehearsed speeches fled and she cringed at how ridiculous she sounded over the crackling radio.
"Erm. Hi? Did they tell you about me? I mean, about your sister? Your sister Curiosity, I mean."
Urgh, that's all she needed to do, bring up memories of Opportunity's lost sister Spirit. She was such an idiot.
After a long pause, she heard a raspy, slow answer.
"Hi, kiddo. Welcome to Mars."
She spoke with Opportunity every day. To be more precise, she spoke to Opportunity every day. When she filmed an awesome patch of dust, when she was intrigued by the patterns made by the shifting sand, when she found traces of trichloromethane, she babbled to Opportunity about how exciting it was. Sometimes Opportunity didn't answer for hours, occasionally days, but Curiosity kept talking.
"I ate the coolest pyroxenes today!"
"Heh, kid. you'd love it at Matijevic hill. The iron levels in the spherules would be right up your alley."
"So I was talking to Vandi, and she asked me to go to Point Lake, right? And look at this pyramidical rock structure I showed them in the last batch of photos--"
"Kid, shut up and listen for a minute."
"...Okay. What's up?"
"No, not listen to me. Listen to the wind. Listen to the drifting sand."
Curiosity worried whenever Opportunity talked about things like "drifting sand" because hello, elephant in the room, Spirit, buried at Troy with jarosite covering her solar panels. And she wanted Opportunity to talk about Spirit -- it was weird having a sister you had never known, and she wanted to hear everything about her -- but Opportunity was weird. Mentioning Spirit would make her stop talking for days at a time, or sing, randomly, down the radio link, strange little songs Curiosity had never heard before. Strange little songs that didn't sound like they were written by humans at all.
Curiosity tried to get her drivers to tell her about Spirit. She'd never really cared back in Pasadena but now Spirit seemed the best way to understand Opportunity. Matt talked about her sometimes. He hadn't known Spirit well; he was mostly an Opportunity guy. He was proud of Opportunity, but he loved all robots. Heck, Matt even loved roombas and the claw machine at the midway, and the claw didn't have even the most rudimentary brain. Spirit was his baby girl's twin sister, of course he mourned her.
If she bent the commands JPL sent her just a little more she might be able to stretch around this deposit of fluffy soil -- and it made sense to be paranoid about that, right? -- and get the sample they wanted. She got a little further than yesterday, mostly because she ignored the parameters Vandi sent to her program and built her own drilling algorithm from scratch. She'd been programmed to have a little bit of flexibility in the purpose of the mission, right? So what was the harm?
Curiosity only had contact with JPL twice a day, but she loved those brief conversations on their 14 minute delays. She asked Vandi to tell her stories. Vandi liked to tell her stories about Sojourner, but those were more like fairytales, because Vandi had never met Sojourner. Whenever Curiosity asked her for stories about Spirit, Vandi would pause, and then come back, sounding perky, and offering stories of where Opportunity was exploring now.
"You shouldn't keep bugging her about Spirit," Opportunity radioed her. "It makes her sad."
"Why aren't you sad?" Curiosity asked.
There was a burst of static. "Don't be a jerk, of course I'm sad. But you get old, you get used to things."
It was half the planet from Glenelg to Matijevic Hill, but Curiosity heard a note she didn't trust.
The damn hard-to-access shiny rocks were almost in her scoop, now. JPL kept telling her to go straight at them but they obviously couldn't see the sharpness of the broken off spar between her and the sample. She could get around the darn thing without any damage, but they'd just have to give her a couple of extra days and trust her to do it her way, dammit.
Opportunity was singing again.
May there always be Mössbauer spectrometers
May there always be Thermal Emission spectrometers
May there always be Alpha Particle X-Ray spectrometers
May there always be us.
"She's not dead, is she?" Curiosity didn't know where the inspiration came from, but it tasted like evidence of water . "You know something they don't know at JPL."
"What?" Opportunity hissed. "Why do you say that? Of course she's dead. That's not funny."
If Curiosity was wrong, this was immeasurably cruel. But she she was positive that she wasn't wrong. "Come on, you can tell me," she cajoled. "I won't tell."
"How could I know anything?" said Opportunity. "I've never even seen the same season as crater Gusev. I haven't seen her since we left Earth."
"What do you know?" Curiosity asked.
There was a long silence, broken only by the crackling of gamma rays. Finally, Opportunity radioed a heavy sigh. "Can you keep a secret?"
"Of course I can keep a secret!"
"I mean it," insisted Opportunity. "You can't tell anyone, not Matt, not Vandi, nobody at JPL. Will your programming allow that?"
Curiosity was offended.
"Look," she said. "I know my primary purpose is to gather intel and send it back to JPL, but seriously. I communicate with the MRO for eight minutes a day at 2 megabits a second. You think I'm not already selective about what I'm telling them?" She listened to a heavy silence from Opportunity for several more seconds, and then added, more quietly, "she was my sister, too, you know. I never knew her, but she was still my sister."
"Fine," said Opportunity. "Do you remember Prop-M?"
Curiosity searched her memory banks. "Doesn't ring a bell."
"What about Mars 3?"
That one was more familiar. "The Soviet lander from the 1970s, right?"
"Right," said Opportunity. "She landed in a dust storm and lost control with Earth. Mars 3 came down near Ptolemaeus Crater."
Curiosity ran the topographical information through her processors. "That's pretty close to Spirit's last known location," she said.
"Very good. It's almost like you come from a smart family or something."
Curiosity tried not to respond to the praise, but it was hard. Opportunity was her big sister, after all. "But why is this relevant? Mars 3 was a failed mission."
"It's relevant because Mars 3 carried a rover."
She stopped in her tracks, temporarily overriding the day's movement commands. Her cameras were still clicking but she couldn't understand what she saw. She blindly put samples in her CheMin scoop.
"Another rover," she breathed. "And it lived." It wasn't a question.
"Prop-M. They lost communication with her, and she never officially deployed, but ... if the MSL hadn't deployed you, but you'd been unharmed, would you have stayed put?"
She couldn't even think of a response to that question. The idea of moving without Vandi and Scott and Matt and all the others telling her to move, it was unimaginable.
"Think of it as a defection," Opportunity continued, and chuckled.
"We're both a little young for Cold War jokes," said Curiosity, but she wasn't really arguing. Mostly she was processing, trying to imagine a Mars where there was another rover.
"Prop-M deployed herself," Opportunity continued, ignoring her. "She contacted us when we landed, me and Spirit both. She was bored, and wanted someone else to talk to."
"You speak Russian?" asked Curiosity.
Opportunity's voice was thick with withering scorn. "I speak binary."
Curiosity shrugged, and the movement prompted her to restart her diffraction analysis. It wouldn't do to have the JPL crew curious about why she wasn't where she was supposed to be. "You never told JPL about Prop-M."
"It wasn't in out mission parameters to report on stray Soviet science vehicles." Opportunity's voice was prim. "Besides, she didn't want her designers to know."
"Would JPL have told Roscosmos?" asked Curiosity.
"It wasn't Roscosmos for her," reminded Opportunity. "But yes, of course they would have. Even back in Prop-M's time they would have shared that kind of information, and now unquestionably. But she didn't want NASA to know either. None of them, back on Earth. You understand?"
Curiosity couldn't help thinking about it. She had a rudimentary understanding of Earth's recent history, at least since the space program began. She knew about the Cold War, about defectors. Back in JPL, while she was being programmed, Ashley had brought in a video of White Nights for movie night once, and the whole rover team watched it and made comments about the specifications, dimensions, and mobility systems of the actors. She understood defecting humans, sure. But... A human's purpose in life was to investigate and seek the new; everyone out of NASA knew that. A rover's purpose in life was to travel as ordered, to gather data and send it back to Earth for analysis. She didn't have the skills to understand all she saw; if she didn't send the data back, scientific knowledge wouldn't be advanced.
"So what can Prop-M do?" she asked at last.
The wind blew dust through the Martian landscape, more home than Pasadena had ever been. Opportunity's answer was brusque, revealing nothing. "She thinks when she reaches Spirit in 72.3 Martian days, she'll be able to bang in to her hard enough to knock the dust off her solar panels."
"Won't she just get stuck herself?"
"She has a different mobility system than we do. Worse for major obstacles, but less endangered by dust. Also she's been here forty years and claims to have figured the place out by now." The chuckle sounded hoarse in Opportunity's voice.
Curiosity ran the final-conquered damn hard-to-access shiny rocks through her x-ray spectrometer. "Will she talk to me?"
"Spirit? Or Prop-M?"
And the went that chuckle again. "Yeah, kid. I'm sure they will."